A team of explorers made up of soldiers and scientists travels through a Stargate, an ancient portal to other planets. They use the Stargate to explore new worlds, forge ties with friendly civilizations and protect Earth from hostile forces. The TV series is based on the theatrical film `Stargate'.
SG-1 must face and destroy the replicators that have made their way to Earth. (S4, ep 1)
SG-1 responds to a plea for help from a civilisation that has traced its roots back to Earth. (S4, ep 2)
Anise conducts an experiment on the team members using the Atoneikan armbands which promises enhanced ability. (S4, ep 3)
An incoming traveller, identified as a Jaffa priestess with whom Teal'C once had a relationship, claims to know how to destroy the Goa'uld. (S4, ep 4)
SG-1 fear that they may have fallen victim to an untraceable Goa'uld method of mind control. (S4, ep 5)
During one of the funniest episodes ever made, Jack O'Neill and Teal'c relive the same day over and over after being exposed to a strange alien device. (S4, ep 6)
When the Russians discover a stargate, they turn to SG-1 for help. (S4, ep 7)
Daniel Jackson is captured after an archaeological dig leads to the discovery of a primordial Goa'uld symbiote. (S4, ep 8)
SG-1 find themselves caught between two civilisations attempting to colonise the same planet. (S4, ep 9)
SG-1 awaken in a mine with no recollection of their former lives. Jonah, Therra, Carlin and Tor - as they are now known - have a new set of memories. (S4, ep 10)
Colonel O'Neill meets a strange man who inexplicably possesses intimate knowledge of the Stargate programme. (S4, ep 11)
A test flight of a recovered Goa'uld death glider goes awry, sending Teal'c and O'Neill hurtling into space. (S4, ep 12)
After the death of his mentor, Daniel Jackson is reunited with a friend and a foe from his past. (S4, ep 13)
SG-1 undertakes a mission to disrupt a possible alliance between two powerful system lords. (S4, ep 14)
All at the SGC are shocked when General Hammond announces his retirement. (S4, ep 15)
Ten years have passed since an alien race known as the Aschen saved Earth and cured cancer but Carter discovers the awful truth behind this seemingly infallible race. (S4, ep 16)
SG-1 notice a change in Daniel Jackson after he is reunited with the Harsesis child, Shifu (Lane Gates). (S4, ep 17)
SG-1 travels to a planet where they find themselves transfixed by a beautiful but deadly device. (S4, ep 18)
Carter tries to motivate a promising young cadet by taking her through the Stargate. But a seemingly routine excursion turns deadly when they are attacked by aliens. (S4, ep 19)
Entity: The SGC finds its computer systems under the control of a mysterious force, which then completely takes over Carter's head. (S4, ep 20)
In an episode that marks the directorial debut of Michael Shanks, problems arise for SG-1 when an old acquaintance comes looking for help. (S4, ep 21)
The Tok'ra reunite with SG-1 when the team steals a Goa'uld mother ship. (S4, ep 22)