The team investigates an unstoppable new enemy soldier engineered by Anubis. Dr. Jackson leads a team in search of an alien device in Central America, but gets more than he bargained for.

O'Neill seeks help from a former comrade to rescue Daniel and Dr. Lee, who have been kidnapped in Central America. Carter, Teal'c and Jacob infiltrate Anubis' super-soldier facility.

Earth's secret offworld base is attacked by Anubis' forces, and Major Carter finds herself being hunted by the enemy. General Hammond and Jacob Carter make an unnerving discovery about the Earth-Tok'ra alliance.

O'Neill goes to great lengths to keep the Ancients' knowledge from falling into Goa'uld hands when the team discovers a second repository. The President replaces General Hammond with a civilian diplomat.

Anubis begins a systematic assault on Earth, and the planet's only hope of salvation depends on whether SG-1 can find the Ancients' mythical Lost City.