SG-1 has to deal with a Replicator infestation on a Russian sub on Earth while Major Carter advises the Asgard about combating the menace in their galaxy.

The SGC is contacted by an advanced and embattled alien human civilization seeking military assistance, but their exact reasons for it become increasingly suspect.

The SGC is visited by a Tok'ra named Anise who brings some armbands used by the soldiers of a long extinct race, which are supposed to increase the abilities of the wearers. O'Neill, Carter and Jackson put the armbands on and it increases their physical strength, but it also causes them to make rash decisions. Can they get the armbands off before they cause their deaths?

An old love of Teal'c approaches the SGC and the Tok'ra claiming that her Goa'uld symbiote has been convinced to defect with their help.

When an SG-team member tries to assassinate the Tok'ra leader, it is believed that some of the SGC have been converted into Za'tarc - programmed assassins. The Tok'ra Freya comes to the SGC with Martouf to try and test all SG-team members. But the Za'tarc detector suggests that O'Neill and Carter are actually Za'tarcs. Is this correct and is there another Za'tarc at the SGC?

Col. O'Neill and Teal'c realize they and their friends are trapped in a time loop.

The SGC learn that the Russians have a Stargate of their own and they need the Americans' help with their problems with it that are affecting them both.

While on an archaeological dig at the original Goa'uld home world, Daniel is captured by a young Unas. He tries to communicate with it and slowly builds a rapport. Meanwhile, SG-1 comes to the planet to find Daniel and they soon realise that some of the SG-team members there may have been taken over by Goa'uld. Will they be able to discover which ones in time to rescue Daniel?

On the Enkarans' new home, SG-1 discovers a giant spaceship is threatening the colonists as it terraforms the planet.

The SG-1 team awake to find they have lost their memories. They believe they are workers in an underground power station. They are told that they are helping to preserve life during an ice age. In truth, they are slave labor to a huge domed city above. When Teal'c starts to recover his memory and is given another amnesia treatment, he forgets his Kelno'reem and starts to die. Will the others recover their memories in time to save him?

The SGC is contacted by a strange man called Martin, a conspiricist who believes he is an alien. The question is, how does Martin know about the Stargate and how come he has a gate address and is he being drugged by others?

While testing a new spacefighter made from Goa'uld parts, Col. O'Neill and Teal'c are trapped when a hidden automatic recall function takes over and sends it into space.

When one of Daniel's professors dies in a lab explosion which might be related to the Goa'uld, he comes back to Chicago to investigate what really happened.

Teal'c is on his home planet, Chulak, where there is rebellion among the Jaffa warriors. He is betrayed as a sacrilegious shol'va (traitor) by Rak'nor, son of a Jaffa friend of his father, and handed to Terok, the torturer of system lord Heru'ur. Ignorant of his fate, the other SG-1 members join Jacob in a risky attempt to take hold of a space mine using a Tok'ra ship piloted by Jacob. En route to Apophis' spaceship, the expedition finds out that Teal'c is being offered as a confidence-building present from Heru'ur to cement an alliance with Apophis against the other system lords, which would make the Goa'uld threat more dangerous than ever. They decide to save Teal'c, but their attempt fails. However, Teal'c's resistance to torture and clear conviction that Goa'uld are not gods finally convinces Rak'nor, who now bravely acts.

General Hammond mysteriously retires from the SGC and a new general is brought in, who breaks up SG-1: Daniel and Sam are scientists, Teal'c is with SG-3 and O'Neill commands a new SG-1. O'Neill tries to convince Gen. Hammond to return, but he finds out that someone ordered Hammond to leave or they would hurt his grandchildren. While the others are occupying the new general, O'Neill tries to find out who that "someone" is. Thereto he must place his trust in the one person he hates most: Maybourne.

In 2010, Robert Kinsey is president of a brave new world since he concluded the alliance with the Aschen, a race discovered by SG-1 which lets humanity enjoy its far advanced science and technology, including a vaccine against aging. Sam is now a civilian scientist, married to ambassador Joe Faxon, whose only worry is failing to get pregnant. When she double-checks the Aschen doctor Mollem's computer with Dr. Fraser, who felt superfluous given superior medicine, they discover human fertility is down 90% worldwide in three years. Sam, Daniel and Teal'c turn to retired general Jack, who always warned against handing over technological control, for a daring plan to turn the clock back like general Hammond did once, sending a message to their past with the exact time of a solar flare, which Sam can calculate using the Aschen computer. Only one ingredient is out of their reach: the GDO device to control the Stargate's iris, which is in the White House. Sam implores her husband Joe to steal it, but he has a secret as well as sincere objections.

When a "chosen" boy found on planet Abydos is brought to SGC, he sends a telepathic message, causing Daniel Jackson's personality to undergo disturbing changes. Will the rest of SG-1 be able to solve the mystery of the boy's origin before he becomes a power-hungry warmonger?

SG-5's Lieutenant Barber commits suicide by jumping into the Stargate shortly after a mission on a planet where a palace abandoned by the Goa'uld about 200 years ago is being studied by Daniel. Soon after, Daniel develops violent mood swings and is committed to a hospital with a neurotransmitter brain condition, presumed fatal after all the other SG-5 members die. Meanwhile, SG-3 has visited the planet, finding only the light installation Daniel reported as particularly fascinating and a human teenage boy, Loran, who hid from Daniel's expedition, but now tells Jack he was left there by his parents, scientific researchers. Back in SGC, Jack also develops symptoms. Sam and Dr. Fraiser conclude that it must be some addiction linked to the light, so when Daniel is nearly terminal Jack, who might not have been exposed too long himself, must bring him back. Jack insists they try turning off the light, and leans on Loran, who is looking for a father-figure; he even gives Teal'c an early "birthday present," but has a dark secret.

Carter decides to inspire a brilliant but difficult Air Force cadet by introducing her to the SGC program.

When the SGC probes a new planet, an alien energy entity there responds by invading the SGC's computer systems, and then Major Carter herself.

On Juna, SG-1 gets a hostile welcome from the local warriors' leader Darian, who seems incredulous they even dared to return. They loyally deliver Sam and Teal'c to Cronus and told them to bury the Stargate. Cronus orders Darian to decapitate Daniel by staff weapon- to find his head is robotic. Cronus's obvious astonishment makes Darian doubt his divinity. At the SGC, Harlan urge them to go on a mission. The master robot-creator tells SG-1 that the robot versions of them he created need to recharge after 48 hours. In order to prevent the Goa'uld gaining access to their duplicates' memories, SG-1 reluctantly go to Juna. Darian now joins them, but feels most of his people won't dare challenge Cronus. The two Teal'cs concentrate on revenging the original's father by attacking Cronus recklessly, while the Sams and Jacks deal with the military problems and overthrowing the Goa'uld rule.

SG-1 delivers their newly confiscated Goa'uld mothership to help the Tok'ra evacuate their planet and deal with their disinformed Goa'uld spy in their midst.