SG-1 departs on a mission only to find themselves in the missile silo where SGC Command was built upon, 30 years ago. Due to solar flare emissions warping the Stargate wormhole, they've traveled back in time. Captured by the U.S. military and unable to tell them anything without altering their own history, they must escape with the help of their commander, General Hammond (now only a Lieutenant, and 30 years younger), and somehow gain access to a Stargate and reverse the procedure so they can return to their own time.