When a mysterious, duplicate Daedalus appears in orbit over Atlantis, the team is dispatched to investigate. Once aboard the deserted and severely damaged ship, the team discovers an ominous video message from the former captain. But before they can make sense of the situation, the ship is propelled into an alternate reality.

As McKay tries to figure out what is going on, the ship continues to jump through various alternate realities, encountering an alien armada and the blistering heat of an expanding sun. Worse, the team realizes that if they don't find a way back to their reality soon, they risk being lost forever.