When powerful aliens come through Earth's Stargate, Colonel Jack O'Neill returns to Abydos to retrieve Daniel Jackson, who has discovered that the alien transit system includes much more than the two planets.
Members of SG-1 become infected with an alien virus that turns them into primitive beings. Dr. Fraiser must find a cure to save the team and the alien population from whom it was contracted.
Pressed by the government to acquire new technologies, SG-1 is led to a world inhabited by a seemingly primitive race. When Apophis arrives, SG-1 ambush him with disastrous consequences.
SG-1 discovers a race of attractive people who age extremely rapidly. The situation becomes personal when O'Neill begins to suffer from the same accelerated aging, and must live out the rest of his life on the planet.
Teal'c and O'Neill are transported to an underground cage designed by the Asgard to protect an alien world from the Goa'uld. Teal'c cannot escape the labyrinth while his larval Goa'uld lives.
SG-1 tracks down Catherine Langford's fiance, who took the first Stargate trip in 1945, and discovers an ancient meeting hall that may hold the secrets of the universe itself.
The banished Goa'uld Hathor is found in an ancient sarcophagus Earth, and takes over the S.G.C. with hopes of raising a new army against the System Lords.
A mysterious affliction wipes out the entire population of a planet, plus an SG team – except for one young girl. Carter befriends her, but learns that she is being used by the Goa'uld.
Teal'c must stand trial for a crime committed while he served as first prime of Apophis when a villager on an alien world identifies him as the Jaffa who killed his father.
The SG-1 team rescues a group of advanced humans from a planet near destruction, and must find a new home for the refugees before the Pentagon gets their hands on them.
Colonel O'Neill and Captain Carter are separated from Jackson and Teal'c during a Stargate journey, and are trapped on a desolate ice world with no way of escape.
When SG-1 visits the underground warehouse of an advanced alien civilization, the area's caretaker transplants their minds into robotic duplicates – a "gift" of immortality.
An alien artifact transports Daniel to an alternate reality, where he is not a part of the Stargate program and the Goa'uld – led by Teal'c – are invading Earth.
Senator Kinsey arrives at the S.G.C. to investigate the program and determine whether the great drain on the U.S. budget is worthwhile, prompting the team to recall missions from the past year.
