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, Daniel and Mitchell race back to Earth, only to emerge from the gate inside the hold of a derelict WWII ship lodged in the Artic ice. They soon realize that Ba'al must have gone back in time and captured the ship that was to bring the Stargate to America, thereby erasing the Stargate program from history. As they try to convince the authorities that they must find a way to set things right, a fleet of Goa'uld motherships arrives in orbit, led by Ba'al, his queen, Katesh (Vala), and his first prime, Teal'c. SG-1 must get to the Stargate and find a way to return the timeline back to normal, otherwise the world will be divided up among the Goa'uld System Lords, and enslaved forever.