Daniel is plagued by dreams of his former girlfriend, who has been taken as a Goa'uld host. Samantha Carter begins a romantic relationship with a detective, from whom she must hide her life at Stargate Command.

Carter and Teal'c go in search of the Asgard to try and save Colonel O'Neill, but discover that the Asgard's enemy has returned with a vengeance. The System Lords seek an alliance with Earth against a common enemy.

While the Goa'uld threaten to attack Earth, SG-1 and the Asgard make a last, desperate stand against the Replicators, which have captured Major Carter and invaded the last outpost of the Asgard civilization.

Teal'c becomes the chief suspect in a murder investigation after he moves into an apartment off-base. Carter considers her future with Pete.

While Daniel finds himself in a mysterious diner suspended between death and ascension, Jacob's fate takes an unexpected turn, Jack and Sam consider their romantic lives, and Anubis unleashes his plan for galactic destruction.