Carter and Teal'c go in search of the Asgard to try and save Colonel O'Neill, but discover that the Asgard's enemy has returned with a vengeance. The System Lords seek an alliance with Earth against a common enemy.

While the Goa'uld threaten to attack Earth, SG-1 and the Asgard make a last, desperate stand against the Replicators, which have captured Major Carter and invaded the last outpost of the Asgard civilization.

The S.G.C. is put under quarantine after a mysterious infection leaves a Russian officer in the infirmary -- but the disease may not be a disease at all.

General O'Neill tries to settle into his new job, but faces never-ending crises - including the capture of SG-1 by the Goa'uld.

Daniel is stranded on another planet after the team's arrival on an alien world sparks a violent civil war.

Teal'c is trapped in a virtual reality simulation, in which he must defend the base from a Goa'uld super-soldier incursion.

Teal'c becomes the chief suspect in a murder investigation after he moves into an apartment off-base. Carter considers her future with Pete.

A businessman threatens to expose the secrets of alien life to the world, forcing Stargate Command to bring him into the loop.

The impending wedding of his son is the least of Teal'c's worries when the Hak'tyl plan an uprising against the Goa'uld Moloc, driving a wedge between Teal'c and Ishta.

The Stargate is stolen, leading SG-1 to discover that the Trust has taken control of an advanced ship in orbit. Teal'c investigates a series of wide-spread Jaffa deaths.

A duplicate of Colonel Carter seeks help from Stargate Command in defeating the Replicator Fifth, who she claims has found a way to counter the Asgard's new weapon.

After the Prometheus responds to a distress call from a Goa'uld ship, Daniel Jackson finds himself a captive when Earth's ship is stolen.

SG-1 comes to the aid of a world about to be invaded by the Goa'uld, only to discover that the local king is Earth's Harry Maybourne.

Relations between the U.S. and Russia are strained when Russian military leaders claim that the U.S. government has been compromised by the Goa'uld.

Jack is confronted in his home by an irate barber...who claims to know everything about the Stargate project and SG-1.

The Replicators begin a systematic attack of the Goa'uld, forcing Baal to come to Earth for help. The Jaffa Resistance risk their entire movement in an attempt to retake a holy city in Baal's domain.

The fate of the galaxy hangs in the balance as Sam and Jacob search for the only weapon capable of stopping the Replicator onslaught. O'Neill leads a defense of the S.G.C., while Daniel squares off against Replicator Carter.

While Daniel finds himself in a mysterious diner suspended between death and ascension, Jacob's fate takes an unexpected turn, Jack and Sam consider their romantic lives, and Anubis unleashes his plan for galactic destruction.

With the timeline changed by SG-1's actions in the distant past, an alternate version of SG-1 must use the newly-discovered time ship to set things right.