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.

O'Neill and Lieutenant Tyler are ambushed by Goa'uld forces and trapped behind enemy lines -- while the rest of their team discover they don't know who Tyler is.

SG-1 is called to defend the people of Abydos from the Goa'uld once again when they learn that Anubis, in search of a powerful device, is about to attack.