During an off-world assignment, Jack is struck down by energy from a blue crystal... which creates a duplicate of him that returns to Earth in Jack's place.

Pressed by the government to acquire new technologies, SG-1 is led to a world inhabited by a seemingly primative race. When Apophis arrives, SG-1 ambush him with disasterous consequences.

Teal'c returns to Chulak to stop his people from implanting his son with a larval Goa'uld.

Daniel is taken captive by an alien with a hidden agenda, while SG-1 is made to believe he is dead.

The members of SG-1 arrive on P3X-989 and are knocked unconscious. They wake up and return to Earth only to find that they are not quite themselves.