An alien artifact transports Daniel to an alternate reality, where he is not a part of the Stargate program and the Goa'uld -- led by Teal'c -- are invading Earth.

Carter must help keep a promising young cadet from throwing away a future at the SGC. O'Neill and Teal'c encounter a dangerous life form at an offworld research base.

SG-1 trains a team of raw cadets, and Colonel O'Neill is forced to take them into a real-life battle situation when he learns of a possible alien incursion at the SGC.