While SG-1 attends a Tok'ra extraction ceremony for Ba'al, the last of the Goa'uld System Lords, Teal'c and Vala inexplicably disappear into thin air. Carter, Daniel and Mitchell race back to a world where history has been changed: the Stargate program has been erased from the timeline. As they try to convince the authorities what's happened, hundreds of Goa'uld motherships arrive in orbit, led by Ba'al, his queen Qetesh (Vala), and his first prime, Teal'c. The remaining SG-1 members must find the Stargate and set things right before the world is enslaved by the Goa'uld.
Writer Brad Wright has stated that this movie will be a stand alone and it's hoped it will launch a continued series of movies based on the SG-1 TV series. Wright also stated fans can expect many guest stars including characters that have been "killed off" (and ones that have gone "off the radar", not dead) during the TV run