While SG-1 attends the execution of Ba'al - the last of the goa'uld system lords - Teal'c and Vala inexplicably disappear into thin air.
Carter (Amanda Tapping), Daniel (Michael Shanks) and Mitchell (Ben Browder) 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, a fleet of goa'uld motherships arrive in orbit, led by Ba'al, his queen, Katesh (Vala) and his first prime, Teal'c.
SG-1 must find the Stargate and set things right before the world is enslaved by the goa'uld.