A replicator survived the fiery destruction of the Beliskner in the atmosphere (at the end of the preceding Nemesis). It swims aboard a Russian attack submarine, kills the crew, and begins replicating itself. Meanwhile, it has taken one week to connect the second stargate at SGC. Not long after, Carter, O'Neill and Teal'c return to Earth, with news that the Asgard came and retrieved Thor shortly after they escaped the crashing Beliskner. As O'Neill prepares to leave on his fishing trip, the Pentagon informs SGC about the Replicators on the Russian submarine, and SG-1 is assigned to deal with it. Before they depart, however, Thor comes through the stargate and asks for SG-1's assistance in stopping a trio of Asgard ships that have been overrun by Replicators and are heading toward Thor's homeworld. Carter returns with Thor to his homeworld, as the rest of the team departs for the Russian submarine—which has been towed to port by a US warship.

While the outcome is expected, the fun, and strength of this episode is the journey to the conclusion. The production team were able to film inside a real submarine, and the episode is all the more impressive for that. We get some pretty terrifying, atmospheric and tension-filled shots that would fit right into the Aliens film! We also get a glimpse at how much more advanced the Asgards are over Earth, and the admission that the Replicators are even more advanced as they change Asgard technology beyond even Asgard understanding!

Jackson is more active in this episode, as they continue with the art-imitating-life appendectomy story. He is given the sorry task of remotely watching O'Neill and Teal'c risk their lives in combat inside the submarine, as well as giving the order to destroy the sub, with his friends and teammates still inside! Nevertheless, the highlight of the episode is SGC's admission that their cover story for the crashing Beliskner isn't sufficient, and that the Russians are strongly suspecting something. This bodes well for some substantial changes in the Earth-side dynamics of the Stargate Program—not only will SGC have to deal with US politics and politicians, but also Russian interests... and possible other international concerns, too.

When O'Neill arrives at SGC, he finds out that someone has dialed the stargate five times in the past hour and a half. The next time they dial in, SGC is able to establish radio contact, and they discover that it is a race of transplanted humans "calling home". SGC learns that the people are from the nation-state Euronda, and are losing a war against a rival nation. SG-1 is dispatched to offer humanitarian assistance, and negotiate for trade. Arriving, they learn that the Euronda live in an underground base protected by an energy shield that is running out of power. They also discover that the Euronda have advanced technology—approximately 100 years more advanced then that on Earth—and they are willing to trade it for a steady and large supply of deuterium. O'Neill leaps at the opportunity, but Jackson resists, strongly suspecting that all may not be what it seems with their newfound allies.

The Other Side is a gem of an episode, one that stays with the viewer long after its finished. At its heart it is a morality tale: how far are you willing to compromise your moral beliefs in order to get what you most need and desire—in this case it's advanced shield technology to defend against a foe that the people of Earth have no defence against. The other side in this Faustian bargain is a group of supremacists committing racial genocide against everyone else on their planet.

The highlight of the episode is two pronged: guest star Rene Auberjonois's convincing portrayal of a leader in desperate times who makes no bones about how he feels about Teal'c—not that he's an alien Jaffa, just his skin colour—and Jackson's protests about rushing into a deal with circumstances they know nothing about as well as the self-discipline he displays with his military comrades who are prevented by their zeal or the chain of command from listening to their moral compasses. Perhaps the oddest touch, and one that highlights that the team isn't on Earth, is the oddly shaped "alien" glasses that their Euronda hosts use to toast their new allies. While it may not have as much humour or action as some episodes, if someone asks what Stargate SG-1 is about, this one should be very high up on the list of episodes to show them.

The Tok'ra archaeologist Anise gates to SGC with recently unearthed high-tech armbands that apparently enhances every natural ability of the person that wears them. However, the Tok'ra can't use them, as there is something about their physiology that rejects the devices. SG-1 is roped in to serve as guinea pigs. Soon after putting the armbands on, they start exhibiting such things as super strength and speed, but also—amusingly—the ability to read a thick book within minutes, among other chuckle-inducing feats. The only trade offs appear to be an almost constant need for "snacks", and that their judgment is impaired, almost like they are under the influence of a narcotic. However, trouble soon multiplies when not only is it impossible to remove the armbands when Hammond orders the suspension of the experiment, but the Tok'ra ask that SGC use their newfound super-soldiers to destroy a powerful new battleship that Apophis is building!

Upgrades is a great 'what if' story, that looks into what our heroes would do if they became all powerful. While some things are cliches—Jackson finally being able to fight back when pushed around by a bully—the real fun is seeing what powers our heroes truly desire in action. With Jackson, that's being able to read something like a 500 page books in seconds! Seeing our heroes not fully in control of their actions is also refreshingly different.

The only real drawback with the episode is the negative portrayal of the Tok'ra. They come across as exploiting the alliance with Earth and having a complete lack of concern for any Earth personnel that they get to help in completing their agenda. However, that 'drawback' is still a credit to the episode—and the series's—excellent writing. All in all, while tackling some serious developments in the series, this episode is lots of fun, and full of great comedy.

After receiving Bra'tac's iris code, SGC is surprised when the Jaffa priestess Shau'nac arrives. More surprisingly, she claims that she has found a way to communicate with the larval Goa'uld in her belly, and has convinced it to join the Tok'ra and tell them the secrets of the Goa'uld! Teal'c appears to have had a previous romantic relationship with Shau'nac—before she became a priestess—and still harbours feelings for her. However, he and SG-1 are skeptical about what she claims. As her larval Goa'uld is fully mature, they are forced to contact the Tok'ra right away, as the risk to Shau'nac's life increases the longer she carries the Goa'uld. Teal'c, however, remains skeptical and attempts to contact his larval Goa'uld in the same manner Shau'nac did, and is troubled by what he discovers.

Crossroads digs into the relationship between the larval Goa'uld and their Jaffa hosts. The short version is that it is little more than a transactional relationship: the Goa'uld get sustenance and a safe place to mature, the Jaffa get enhanced healing and long life. However, what's much more disturbing is how callously the Goa'uld treat their juvenile brethren, especially considering the devotion the juveniles display for their race... or at least the branch headed by the 'mother' that spawned them. So that safe place takes on a meaning of luck—who the Jaffa serves under, what assignments they're given, and the skill and cunning of the Jaffa themselves to get out of sticky situations alive!

Teal'c comes across as a bit of cad in this episode. Isn't he still married? Apparently lines were written that indicated he was divorced; not surprising after what his wife did in Family. However, they were cut from the shooting script and it leaves the viewer scratching their head over Teal'c's inexplicable morality change—that he isn't keeping the promise inherent in his wedding vows. Ultimately, the episode is less about delving into Teal'c's past and more about establishing a new enemy for SG-1... one who is deep inside the Tok'ra ranks.

SG-1 and a handful of personnel from other SG teams are on Vorash finalizing a treaty of alliance between the Tok'ra and the President of the United States. When the Tok'ra Supreme High Councillor enters the room, Major Graham starts firing at him with a Goa'uld weapon, killing several Tok'ra and another SGC member. Unable to control himself, Graham activates a self-destruct mechanism on the weapon and dies. Anise, the Tok'ra scientist from Upgrades and Crossroads believes that Graham was a za'tarc—an unwitting assassin subconsciously programmed by the Goa'uld. They began appearing in the past 2 months, and this is the first time the victim was a human. Back in SGC, they realize that the Tok'ra-Earth summit is in danger, as there might be other Tok'ra or SGC personnel that have been compromised by the za'tarc brainwashing. Anise presents a method that she believes will detect a za'tarc, and they begin testing base personnel. Problem is, in addition to a member of Graham's SG team, both Carter and O'Neill are flagged as za'tarcs!

Divide and Conquer is less about getting to the bottom of the brainwashing, and more a thriller: who is or is not a victim of the brainwashing, and can they find and stop that person in time. Due to that, it is a bit more frustrating than usual, as the story hardly goes beyond giving subtle hints on the perpetrator—who may or may not be covering their tracks with false images! On the other hand, the episode eventually gets around to dealing with Carter's and O'Neill's romantic feelings once and for all.

Due to the way the episode revisits recent episodes, there are times when it feels like a clip show. On the other hand, it does fill in some blanks in Upgrades—how Jackson deals with a Jaffa guard is a hilarious blink-and-you-miss it scene! Alas, the episode is lighter on humour than usual. Sadly, it is also the episode where Martouf is killed off. It's a bit of a point of frustration, as the character had a lot of potential that hadn't been mined yet. All-in-all, the episode leaves a bit of a bitter aftertaste despite its revelations, probably because it asks too many questions with the za'tarc complication, and doesn't answer enough of them.

SG-1 are investigating ruins that surround a stargate on a desolate desert planet. While Carter is busy setting up a science station to study the unique coronal mass emissions coming from the hot sun overhead, O'Neill is bored out of his mind. Jackson, on the other hand, is busy trying to decipher the text on the ruins with the assistance of Malikai, a non-Earth human archaeologist who has been studying the world for many months. When the star's emissions reach their peak, however, Malikai stuns the surprised Jackson with an energy weapon. Malikai activates the alien device he has been working on, and energy beams start shooting into the stargate. O'Neill and Teal'c rush over to stop him and then—after a flash of light—O'Neill finds himself sitting in the SGC cafeteria eating fruit loops. Before long, he realizes that they are stuck in a time loop, and that only he and Teal'c are aware that everyone is repeating the same 10 hours!

Window of Opportunity is an intriguing episode full of great fun. In the early passages, we see O'Neill and Teal'c more-or-less squirming as they are forced to suffer through the exact same medical tests as no-one believes them. Later, the episode takes on aspects of the film Groundhog Day as we see O'Neill and Teal'c not only memorizing historical and scientific facts that are way out of their element, but also learning a long extinct language, among other things. The episode then takes it into the extreme when O'Neill and Teal'c realize that they can get away with things that they could never ordinarily do.

While those bits are what make this episode very memorable, the highlight are the scenes where Carter and Jackson either slyly comment on O'Neill's poor reading habits or are flabbergasted that O'Neill and Teal'c suddenly start using advanced jargon—correctly, they note. Perhaps the only drawback is that the episode ends its fun premise sooner than we would like. I'm sure that Teal'c and O'Neill could have found more ways to abuse and exploit their unique circumstances—just how many billion miles did that golf ball fly?

SG-1 are ready to embark on a new mission, but the final chevron just won't lock and the gate doesn't dial. All diagnostics indicate that the gate is working fine. Carter soon works out that not only has Russia recovered the stargate that was lost in Nemesis, they are actively using it. The problems mount when the Russian gate doesn't close after the 38 minutes that the stargates usually automatically close at. After confronting the Russian government, they admit that Russia has a working gate, it is connected to another world, and it cannot be closed. Russian scientist Dr. Svetlana Markov—one of the senior members of the Russian stargate program—convinces her government to allow SG-1 into their secret facility to help resolve the problem. Soon after arriving, however, SG-1 and Markov discover not only the active gate, but that all 47 people assigned to the base are dead!

Watergate is an intriguing episode. First and foremost it lays the groundwork for the stargate program to expand not only to Russia, but internationally. It also has the high-concept idea of a world completely submerged that is not only accessible only by submarine, but is populated by aliens that are virtually indistinguishable from water. Round it out is Marina Sirtis as Dr. Markov—a role that showcases her acting abilities; any suggestions of or similarities to her preceding staring role completely disappear in her performance.

Another highlight of the episode is the bigger scale that the production team was able to add to the series in the fourth season. Here we are treated not only to a crane shot up, over, and down the other side of a C-130, we also get interior shots. On top of that, there are wonderful shots of a submerged Greco-Roman city, and shades of The Abyss with vital scenes set in submarines with aliens who have mastered water so well, they can prevent it from flooding through an open window. Rounding it all out is the reappearance of Colonel Maybourne—the antagonist we love to hate—inside a freezer, frozen solid! What's not to like?

Jackson and Dr. Robert Rothman (Forever in a Day, Crystal Skull) are on a 3 week archaeological dig with SG-11. The fossilized Goa'uld symbiotes that they have unearthed lead them to suspect they are on the planet that the Goa'uld parasites originally evolved on. As they bag their latest finds for further study, a large creature bursts out of the nearby woods, kills a soldier, and makes off with Jackson after knocking him unconscious. Rothman races back to the stargate—and SGC on Earth—while the rest of SG-11 go in search of Jackson. SG-1 and SG-2 are promptly assembled and launch a rescue mission. Meanwhile, Jackson awakens and finds that he's the prisoner of a primitive Unos. Not only that, he fears that he has become the evening meal!

On its surface, The First Ones appears to be "rescue Jackson from the primordial Goa'uld monster of the week". However, it is far deeper than that. In addition to the series taking its first hard look at the origins of the Goa'uld parasites, it also delves into who and what the Unos are when they're not under the control of a Goa'uld symbiote. However, the real heart of the episode is Jackson—even in the face of his own demise, he can't help but continue his scientific investigations, as well as attempt to build a diplomatic bridge with a creator that initially seems to not speak any intelligible language!

Michael Shanks's performance is the highlight of this episode. We really feel the pains and duress he is under, as well as his overpowering intellectual curiosity and will to make peace and build friendship above all else. Teal'c is another standout part of this episode, and a source of surprisingly funny humour. Take, for example, this exchange: "Trust in me, O'Neill." "What if I'm not O'Neill?" "Then I was not talking to you." Christopher Judge's faint wink-wink nudge-nudge and Richard Dean Anderson confused raised-eyebrow response really transform those lines. Nevertheless, it all underscores the best things about the SG-1 series: mystery, danger, humour, action, villains you can't help but love to hate, and excellent writing.

A month after SGC has successfully resettled the Enkarans—first mentioned in Watergate—SG-1 goes to visit. The lush, uninhabited planet is just right for the Enkarans, as they need a really thick ozone layer or else they'll go blind due to UV light exposure. A feast to celebrate the successfully relocation is interrupted when a young man comes running from a nearby settlement telling everyone of a terrible danger. SG-1 goes to investigate, and discovers a giant alien ship slowly moving over the planet's surface, destroying everything that passes under it in an energy curtain. It's up to SG-1 to find a solution, but without military support (General Hammond refuses to authorize it) and time (it took two weeks to relocate all the Enkarans), they are in a really bad spot.

Scorched Earth both really challenges our heroes, and highlights how their diverse capabilities complement each other and make them an even more effective team. The hero of the episode is Jackson, who not only disobeys a direct order to save the day, but doggedly pursues a diplomatic, negotiated settlement that works for everybody. On the other end, we have O'Neill who is not only looking out for the greater good, but doing his best to protect the team. This is underscored in the scene where he orders Carter to turn the Naquadah reactor into a bomb—she disagrees with what creating that option for O'Neill means, but as he takes full responsibility for it, it protects her morally.

The weakest part of the episode is the reaction of the Enkarans to the threat. While it's inevitable that SG-1 will be involved, given that the Enkarans were apparently recently freed—or escaped—from the Goa'uld and possess the skills to assemble modern steel buildings within weeks, one would suspect that they are technologically advanced enough to at least assist SG-1 if not try to come up with their own solutions. On the other hand, the high point is Bryan Markinson's portrayal of Lotan, a copy of the Enkarans that was assembled on the giant alien ship to act as a negotiator between it and the people on the planet. Markinson finds the right balance between a robotic-like newly created being trained by an AI, and a curious, emotional being open to alternatives and capable of growth.

The SG-1 team is doing hard labour in an underground facility. Lining up to receive their afternoon meal, O'Neill and Jackson get into a scuffle. Teal'c intervenes, and shouts out their names and that they are part of SG-1 and don't belong there. The other three are baffled, as they refer to themselves as "Jonah", "Therra", and "Karlan". Teal'c—referred to as "Tor"—is dragged away, and disappears for one week. Jackson begins dreaming about the stargate, and wonders if he was once friends with the other three. When Teal'c returns, Jackson asks him about it, but Teal'c bluntly replies that he was "night sick", doesn't know Jackson, and doesn't want Jackson to talk to him ever again. However, Jackson continues to be skeptical and cautiously persistent in his search for the truth.

Beneath the Surface starts with a cold opening, where we don't know what's happening, nor how SG-1 got into the situation they are in. Concurrently to exploring their situation, we are gradually introduced to how they got into it via flashbacks. The fact that they have had a "memory stamp" and their current companions are all cautioning them not to dwell on their doubts and suspicions—lest they by labelled "night sick" and disappear for a week like Teal'c—complication things all the more. Concurrently, we have SGC working with the 'above ground' residents of the planet who are claiming that SG-1 disappeared when they went out into the cold wilderness to investigate something they spotted on a nearby glacier. General Hammond being bound by policy and unable to either send in a military force nor severe ties with the planet's rulers is an intriguing frustration.

The highlight of the episode is Don S. David's portrayal of Hammond when he's at wits' end and out of options. David conveys an extraordinary amount in the scenes where he has no dialogue and essentially stares out a window. When he's given dialogue, it's all the more impressive. The episode also has a theme where the SG-1 team members have to give up something to gain something better. On the one hand we have Jackson being forced to choose between his new friend Kegan and befriending Carter and O'Neill and uncovering the truth behind their situation. On the other hand, we have Carter and O'Neill, who are depicted as close friends gradually on the way to something much more than that, and being painfully aware of what they have to give up to return to their real lives. Apparently, in earlier drafts of the script, the relationship between Carter and O'Neill was going to be a lot more clearly romantic in nature. While making it more nebulous works in favour of the overall series, it reduces the emotional punch of this episode to a whimper. Combined with the blatant The Time Machine upper/lower class distinction aspects of this story, the episode comes up a bit short.

SGC receives a bizarre phone call from a man that rambles on and on about one conspiracy theory after another. However, he gets everyone's attention when he mentions not only the stargate by name, but its shape and location. On top of that, he knows O'Neill's name, and asks to meet him. SG-1 is promptly dispatched to Montana—the location where the man wants to meet—under orders to find out what he knows, and how he knows it. The man is Martin Lloyd, a short, bald, goofy guy who appears to be obsessed about conspiracy theories, and resolutely believes that he is being watched, is an alien, and doesn't belong on Earth. SG-1, however, can't just write him off, as he randomly remembers things that are factually correct. His suspicions about being watched also turn out to be true, putting SG-1 into mortal danger by a group claiming to be government agents!

Point of No Return is a fun, goofy episode. A lot of the fun comes from SG-1 being put out of their element on an undercover operation. It also gives Teal'c a chance to explore Earth beyond the confines of SGC, and the fun that Christopher Judge has with that. The highlight, however, is Willie Garson's knockout performance as Lloyd. He strikes the right balance between goofy, obsessive raving, and just enough seriousness that the viewer can't easily dismiss what his character says, as there's usually a kernel of truth buried in it.

The episode is also tinged with sadness, as when Lloyd's true story is revealed, it turns out to be quite tragic. It also further underscores the threat posed by the main Stargate SG-1 villains, and just how lucky the Earth has been—or just how much the heroes of Earth, past and present, have saved it from a horrible fate. Aside from the challenge of deciphering Lloyd, the episode doesn't really dig deeply into any particular issue. Nevertheless, it is a must see, as not only is it one of Stargate SG-1's standout lighter episodes, it also sets up the backstory behind episodes #100 and #200.

SG-1 captured a pair of Goa'uld Death Gliders two years ago (Season 2's The Serpent's Lair). During the intervening years, people at Area 51 have created the X-301—a hybrid attack craft that looks like a Death Glider with a human cockpit added to it. Teal'c performs a demonstration of the vehicle's flight performance while SGC personnel and Pentagon representative Lt. General Vidrine look on. O'Neill joins Teal'c in the cockpit when a live-fire test of the X-301's weapon capabilities is authorized. During the test, however, just as Teal'c lines up for an attack, the X-301 turns skyward and accelerates upwards into space. Its engines cut out, and as the X-301 drifts, the voice of Apophis tells them that there is a recall device in the glider, and the glider is being returned to his home planet! Even before Hammond can finish giving the order to contact NASA to launch a rescue mission, the X-301 has passed beyond the Space Shuttle's range. It's up to Carter and Jackson to contact and arrange help from the interstellar allies that SGC has built up over the years.

The highlight of the episode is the script itself: it is full of circumstances and terminology that are scientifically accurate or authentic. Take, for example, the ever-growing time delay in radio communication that appears as soon as the X-301 rockets into space. After being spoiled by instantaneous communication on shows like Star Trek or even with Stargate SG-1's own Goa'uld Long Range Visual Communication Devices, it is a refreshing change of pace. Messages getting crossed or mixed up due to the time lag adds an interesting wrinkle to the story.

The episode also hints at the countermeasures Apophis introduced after Teal'c's betrayal and continuing counterattacks. It also delves a little deeper into the bad things that are starting to occur due to the strained relationship between Earth and the Tok'ra. It's also always nice to see Jacob Carter, and the shocked reaction of Carter after hearing him say "The technology you're screwing around with is way over your head!" takes the cake. The rescue mission itself also highlights just how close the Goa'uld threat is, as it suggests that a rather hostile System Lord has a rather large number of Ha'tak Motherships less than a day's travel in hyperspace away. Nevertheless, the episode can be a little bit dry at times, as our main "action" heroes are stuck passively in the drifting X-301. While it gives Amanda Tapping and Michael Shanks a chance to take the limelight, some things tend to end up coming across as a little too coincidental or convenient in this adventure.

Jackson discovers that his former archaeological professor and mentor Dr. David Jordan is dead. He returns to Chicago for the funeral and meets up with his friends and former colleagues: Steven Raynor, and Sarah Gardner—Jackson's former girlfriend. Meanwhile, the rest of SG-1 is given long-deserved leave: Carter stays on base to work on personal projects, and O'Neill drags Teal'c to go fishing together. Jackson soon learns that his mentor died in mysterious circumstances involving the recently recovered artifacts from a 'cursed' 1931 expedition to Egypt. As the body count starts to increase, Jackson notices that there is Goa'uld script on one of the canopic jars, and it's twin is missing!

The Curse is an intriguing episode, as it initially appears to be a light episode delving into parts of Jackson's past that haven't been addressed yet, into a thrilling who-done-it mystery and the revelation of a here-to-fore unknown Goa'uld threat. In the process, we get to see the personal effects of Jackson's pre-Stargate theories on his colleagues and friends, and the damage caused by the steps he has taken to protect them from what made him an outcast and the laughing-stock of the archaeological community.

Another intriguing part of the episode is that even though the Goa'uld symbiotes are apparently asexual, they appear to have a gender identity or at least preference. This episode once again has a symbiote of one gender taking a host of a different gender. It also raises such questions as if a symbiote can access all the memories, mannerisms and whatnot of the host, how much does the host subtly (or overtly) influence the controlling symbiote? Nevertheless, the highlight of the episode is the phone call Teal'c takes while 'out fishing' with O'Neill. It's great fun watching the tough-as-nails Jaffa squirming under O'Neill's piercing reaction to the 'intrusion'.

Teal'c is on Chulak continuing his mission to turn the Jaffa against the Goa'uld. He is captured by a pair of loyal Jaffa who were pretending to be rebels. Meanwhile, Jacob Carter is vacationing on Earth (presumably since Tangent brought him back to the Solar System). The Tok'ra contact him about an important mission he must undertake immediately: Apophis and Heru'ur are meeting in the Tobin system to form an alliance. The Tok'ra want to prevent that alliance, and force a conflict between the two super powerful Goa'uld. They plan to do this by reprogramming one of the thousands of mines orbiting the planet Tobin to attack Apophis's ship. The wrinkle is that the mines were made by an extinct civilization based on the ancient Phoenicians of Earth, and although the Tok'ra have the mines' technical manual, they cannot completely translate it. Carter, Jackson, and O'Neill accompany Jacob to help him on his daring mission to finish the translation and reprogram an active mine.

The Serpent's Venom marks a shift in the series. On the one hand, we have Apophis getting stronger and stronger—to the extent that he rivals the combined forces of all of the other system lords. On the other hand, we have some arguably bigger revelations on just how large Teal'c's rebellion has become among the Jaffa soldiers of not only Apophis, but the other Goa'uld as well. The heart and soul of this episode is Teal'c's story. The force of his will and resolve not only prevents his Goa'uld captors and torturers from breaking him mentally, it inspires at least one Jaffa soldier to change allegiances and join Teal'c's rebellion!

The highlight of the episode is the special and visual effects. The production side of the show has evolved to the point that the CG animation is starting to look realistic (or at least at the same filming resolution as the live-action shots.) In this episode, we are presented with the incredible sight of a planet surrounded by a swarm of chaotic and randomly moving mines. However, even that is eclipsed with the reveal of Apophis's new and positively gigantic mothership. Having said that, it's quite remarkable that Teal'c's story is not only not overwhelmed by the effects, but it also helps ratchet up the episode's suspense levels in scenes that are radically different in tone and pacing!

SG-1 return to SGC under heavy fire. O'Neill is unfazed by it, but Hammond states that he's had enough, has had his fill of sending good people into danger, and intends to retire immediately. O'Neill doesn't believe Hammond, and presses him for the real truth. However, Hammond refuses to discuss it. His replacement, Major General Bauer soon puts in place new policies in the SGC. The most pressing is the break up of SG-1: Jackson gets a desk job, Carter is assigned to a project to make a naquadah-enhanced nuclear bomb, Teal'c is moved to SG-3, and O'Neill is left in the lurch. O'Neill soon visits Hammond, and after some pushing, gets the truth behind the General's surprise retirement.

Chain Reaction digs deeply not only into who Hammond is and his personal life, but the relationship he has with the soldiers under his command, and how he has arguably protects them from dangers that come from unexpected directions. On top of that, it delves into the recent actions of the N.I.D.—particularly what they've been up to since Shades of Grey—and brings back a pair of SG-1's nemeses: ex-Col. Maybourne and Senator Kinsey.

A lot of the fun in this episode stems from O'Neill being forced to team up with Maybourne to help Hammond. While they both have their own agendas, its fun watching them them try to outdo each other, and doing their best not to let their momentary partner get the upper hand. While one outcome of the episode is expected—the fate of Hammond—what's more interesting and arguably has a greater effect on later episodes are the fates of Maybourne and Kinsey. This episode highlights that we can't always take the status quo for granted, and that one of the strengths of the series is that our heroes have rivals and enemies hidden even in the midst of the armed forces and government that ought to be completely supportive allies.

10 years in the future, SG-1 and even SGC have been disbanded because the Earth met and allied itself with the Aschen. The alliance has been extremely fortuitous, because not only have they succeeded in wiping out the Goa'uld, the Aschen are sharing their wondrously advanced technology; which has, among other things, effectively doubled the human lifespan. After SG-1, Carter moved on to working on scientific projects with the Aschen. She has also married Joe Faxon, Earth's key negotiator with the Aschen. They are trying to have a baby together, but aren't having much luck. During the ceremony marking the 10 year anniversary of the alliance, Carter meets Dr. Fraiser—who has effectively lost her occupation due to the advanced Aschen medical technology. Dr. Fraiser offers to examine Carter, and they soon discover that the Aschen have secretly sterilized the majority of the Earth's population. Carter sets out to reunite SG-1, as only they know of a way to send a message into the past to prevent this tragic turn of events from happening!

On the surface, 2010 is an engaging tale that has SG-1 overcoming their differences and disagreements, and rising to the occasion to save the Earth. However, underneath the surface is a cautionary tale about the dangers of offers that are too good to be true, as well as a meditation on whether or not it is right to effectively rewrite history. While Stargate SG-1 has never pretended to go as deep into such moral issues as Star Trek, it is still quite refreshing to see the show acknowledge and consider the morality of their actions.

While the episode hints at discoveries and accomplishments beyond our wildest dreams—defeating the Goa'uld is just the starters!—the highlight of the episode is seeing the team get back together, and working together in their own unique ways to collectively solve the problem. Walter "Davis" Harriman's appearance as an "operations technical advisor" at the former SGC facility after it was opened to tourists is also great fun. While it's great to see him outside the operator's chair and doing something proactive to the plot, his treatment by the former members of SG-1 is also a refreshing reminder of how much Stargate SG-1 is not Star Trek!

SG-1 returns to Abydos at the request of Kasuf—Jackson's father-in-law—as he heard a voice saying his daughter's name when a whirlwind came out of the stargate. They find the whirlwind in the desert, and Daniel identifies himself to it. The whirlwind melts away, revealing the young boy Shifu, the Harcesis child that Jackson has been searching for since his wife died. He wants to learn about his mother through Jackson. As Shifu was only a baby when Oma Desala took him into her care only 1 year ago (season 3's Maternal Instinct), SG-1 takes him back to SGC to give him a medical checkup to find out why he aged so quickly. As he apparently also holds all of the genetic knowledge of the Goa'uld, he also carries with him the potential means of one day defeating the Goa'uld. It falls to Jackson to get Shifu to reveal the Goa'uld's technological secrets. The boy agrees to "teach" Jackson, but it's not what anyone anticipates, let alone expects!

Absolute Power is the counterpart to season 3's Forever In a Day, with Jackson being taught a valuable lesson in a dream. While the earlier episode has a positive dream and a negative outcome, the later is the polar opposite. Absolute Power only hints at Oma Desala's powers and how much she has given Shifu (or how much he has learned). However, the focus on the episode is on the Goa'uld—specifically asking questions about 'why' the Goa'uld are evil, and pondering the question in terms of nature vs. nurture. This is further complicated with the arrival of the Tok'ra, who while obviously aren't evil, share some of the Goa'uld's superiority tendencies.

Nevertheless, the highlight of the episode is the young Lane Gates's portrayal of Shifu. He appears stoic and wiser than his years as he speaks the Buddhist-like esoteric riddles in a manner similar to Terry Chen's performance as the Monk of Kheb in Maternal Instinct. At times the riddles are frustrating for the viewer as they are nigh-impossible to decipher, but they are also the source of some of the best laughs in the episode from the baffled responses of the heroes of SG-1. In the grand tradition of great TV, while this episode answers some questions, it ends up asking a whole bunch of new ones.

Jackson and SG-5 are offworld investigating an abandoned Goa'uld palace. Carter is preparing to head through the stargate with SG-5's Lt. Barber to join Jackson. Just as the gate opens, Lt. Barber rushes into the opening gate and is vaporized. Hammond recalls Jackson and the rest of SG-5 while they investigate the apparent suicide. As time passes, Jackson gets more and more irritable. At one point he rushes to General Hammond's office and demands that he be allowed to travel back to the Goa'uld Palace immediately! Hammond declines, as they are due to travel there the very next morning. The next day, however, Jackson doesn't report in. O'Neill heads to Jackson's off-base residence to check up on him, and finds that Jackson's in a suicidal state and about to jump off his balcony to the street far below. The other members of SG-5 are also displaying similar symptoms, which are consistent to drug withdrawal. The only option is to send SG-1 back to the planet to investigate, but as there are no signs of contagion or foreign substances in the affected people, they have no idea what is causing it and go at great risk to themselves.

The Light is an unusual episode in the series. Even though it introduces a new aspect of the Goa'old—via a long abandoned opium den-like pleasure palace—the episode doesn't do anything with it. In addition, while the first time we see our heroes spacing out to the psychedelic light show in the palace's main room, it rapidly wears out its welcome and ends up frustrating and dulling the episode. Due to that, it feels like the episode was a missed opportunity.

The introduction of the young boy Loran, who lives in the palace, also doesn't live up to its initial promise. While his story is troubling and tragic, it doesn't really add anything that we didn't already know about the hidden danger in the palace, nor does he make any big revelations—aside from revealing a control panel at a critical time. As the episode doesn't even get around to addressing why Lt. Barber died (suicide from depression? a mistake from wanting to get back to the palace really badly?) it's fairly safe to give this one a pass.

O'Neill and Teal'c are assigned the unglamorous task of watching over a group of scientists in an offworld research base on a planet (moon) that could ultimately become a permanent base. Jackson is also offworld with SG-11, and doesn't appear this time. Carter, on the other hand, is giving a lecture at the US Air Force Academy. She is introduced to Cadet Jennifer Hailey, who while brilliant, has a major chip in her shoulder and is hard to interact with at the best of times due to her self-righteous attitude. As Carter perceives her potential contributions to the Stargate Program, she attempts to take Hailey under her wing—even after Hailey is threatened with expulsion from the academy for unbecoming behaviour!

Prodigy is an odd episode. On the one hand, the show filmed on location in the real Air Force Academy and even has a guest appearance by the real serving Chief of Staff of the US Air Force! On the other hand, its academy-based story never really gets off the ground—all the pieces for a great story are there, it just doesn't put them together in a way that provides enough lift. The episode's greatest weakness is Elisabeth Rosen's portrayal of Cadet Hailey. While it's an excellent performance, it doesn't 'fit' with what the rest of the characters are doing for her. In short, as Hammond judiciously says at a key point, "Not everyone is cut out to be an Air Force officer."

Nevertheless, O'Neill and Teal'c's offworld 'adventure' makes up for the weaknesses in the A-story. What initially seems to be an excuse to torture our heroes for comedic effect turns into a fairly tense climax that does what SG-1 does best: relies on the contributions of ALL the team members to get the job done. The highlight of the episode has to be when Teal'c offers to Zat O'Neill—you just know something will go wrong from his unfamiliarity with Earth's cultures!

SGC successfully dials an address that they acquired from the Ancients' Repository of Knowledge, and send a M.A.L.P. through to investigate. They see a here-to-fore unknown advanced society. However, the M.A.L.P. is almost immediately taken out of their control and starts sending volumes of data back to SGC. The gate control-room systems are overloaded and begin shorting out, and the only way that they can deactivate the open stargate is to use the emergency disconnect switch—which immediately plunges the base into darkness until emergency power kicks in. However, the transmission was more than just raw data. It is an apparently living AI or other highly intelligent and adaptable computer virus, which has been tasked with eliminating the threat posed by the human race!

Entity has an intriguing setup, presenting us with a rarity in the series: an extremely advanced society completely unrelated to any other group that has been encountered before. The twist that they'd rather be left alone and transmit an entity to make sure that happens is also thought provoking. However, after the initial attempts at communication with the entity, the episode falls back on well used tropes—some of the themes may not have been used on the Stargate SG-1 series before, but have in other SF series; the movies Terminator 3 and Virus come first to mind.

Nevertheless, the episode does a good job with the material, mining it for plenty of character exploration and growth. It also raises salient points on both sides of its core argument over how to respond to the entity: attempt to make peace or do what it takes to protect ourselves. The highlight is Amanda Tapping's performance of Carter after she has been taken over by the entity—the synthesized voice that it uses to communicate adds significantly to her creepy, inhuman blank stare and rigid posture. The choice that O'Neill has to make at the end is also thought provoking. While the episode ultimately makes use of a reset switch, it's not a complete one and leaves room for potential ramifications in O'Neill's future relationships with his teammates.

SG-1 arrive on the planet Juna and are immediately attacked by Jaffa and local warriors. The leader of the local warriors, Darian, recognizes SG-1, calls them by name, and tells the Jaffa that SG-1 are the ones that led the locals in the rebellion against Heru'ur. The Jaffa belong to Cronus, who subsequently came and conquered the planet. SG-1 has no memories of those events. As they are imprisoned and led away, O'Neill escapes. On Earth, SGC receives an unusual iris code: "Comtrya". SG-1 (not the ones on Juna) recognize it as the greeting used by Harlan, and Hammond lets him come to Earth. Harlan tells them that their artificial copies (season 1's Tin Man) have been going on missions for the past few years, and have not returned from their latest one to Juna. Hammond, being concerned about the secrets they have about Earth, sends SG-1 to their rescue.

Double Jeopardy is another tour de force. On the one hand, we have the initial mystery of SG-1 apparently returning to a planet that they have no memory of having previously visited. On the other hand, we get the alarming revelation that the Goa'uld may be re-invading planets that SGC has previously helped liberate from the Goa'uld! In addition to that, we get Carter, O'Neill and Teal'c interacting with copies of themselves. O'Neill's is the most hilarious, and one wonders how much fun it would be to see that on a semi-permanent basis.

The drawback to the episode is that Jackson hardly appears. However, that's quite understandable, as Michael Shanks had more than his hands full directing this episode! Nevertheless, his limited appearance does imbue this episode with a surprising, shock twist! The icing on this episode's cake is the return of Cronus—one just knows that he's on a collision course with Teal'c, and that in itself is just one aspect of this episode's immensely satisfying conclusion.

SG-1 takes the Ha'Tak mothership that they acquired (in the preceeding Double Jeopardy) to Vorash, as the Tok'ra have asked to use it to transport themselves and their stargate to a planet off of the Goa'uld's map of gates. Tanith, the Goa'uld spy in the Tok'ra's midst that killed Teal'c's lover (in season 4's Crossroads), is surprised to learn of the plan, and that he won't be going with the rest of the Tok'ra—as they were aware from the start he was working for Apophis, and have been feeding him false information for the past year. Tanith escapes and contacts Apophis, who immediately launches an attack fleet to wipe out the Tok'ra. Learning of the impending attack, Carter and her father Jacob come up with an audacious, extremely risky plan that may see them rid of Apophis once and for all.

Exodus takes things up a notch and sees SG-1 set their sights on something even more extreme and ambitious than what we've seen in the show so far. One can almost see the writers brainstorming: "We've rescued the Earth, we've blown up Hell... how can we top that?" Alas, the episode doesn't invest enough time in Teal'c's story arc of getting revenge on his lover's killer, which tends to inhibit the episode from building up much tension at all. Perhaps it's because the backstory of Teal'c's relationship with his lover wasn't strongly developed in the first place, or perhaps it's because Tanith's character itself isn't on the same scale of wicked villains that we love to hate—like Apophis or Kronus. While Peter Wingfield plays placid Tanith extremely well, there's not enough contrast between him and Teal'c's restrained personality. Perhaps a showdown with the excitable O'Neill would have resulted in more fireworks?

As it is, the highlight is watching O'Neill get ever more frustrated as he loses control of the situation as Teal'c goes off script on his mission of revenge. Jackson and Carter also get their moments to shine as they are frustrated by their own situations—Jackson minding the bridge of a starship that he can't control, and Carter forced to repair a Goa'uld hyperspace engine that she has had no prior experience with. Nevertheless, when the action starts, it goes big. The twist at the end with the protagonists figuratively being dropped from the frying pan into the fire is probably the most shocking development in the episode. However, as the episode hasn't invested enough in the buildup of the character aspects, it ultimately doesn't have as much panache as the episode's plot ought to have.