The Stargate is an intergalactic gateway, developed by an ancient civilization, that links other planets from other solar systems to ours. The U.S. Air Force assembles a Stargate team headed by Colonel Jack O'Neill for interstellar peacekeeping missions.

SG-1 searches for an ancient weapon which could help them defeat the Ori, and discover it may be in the Ori's own home galaxy. As the Ori prepare to send ships through to the Milky Way to attack Earth, on board the Odyssey, SG-1 travels to the Ori galaxy. The International Oversight Committee has their own plans and SG-1 finds themselves in a distant galaxy fighting two powerful enemies.