When an alien scientist activates a device that the Ancients created for time alterations, Jack and Teal'c get caught in a time loop.

An archaeological team makes an amazing discovery - a planet holding primordial Goa'uld symbiotes. But the planet also is home to the Unas, the first race that acted as a host to the symbiote, and the team and SG-1 are soon in danger from the symbiotes.