 The team finds another version of themselves , dead , who come from yet another parallel universe and were trapped aboard while investigating the ship , just as they are . Soon , the ship jumps again , into a reality where Atlantis is under attack from an unfamiliar alien ship . Sheppard intervenes , and the aliens retaliate by launching fighters . One of the fighters crashes into the Daedalus before it jumps again , this time into a universe where Atlantis ' sun has already swelled into a red giant . To keep the ship from being burned up , McKay ( David Hewlett ) increases the rate at which the alternate reality drive activates , warning that his modifications are irreversible . Meanwhile , the team must contend with aliens from the crashed fighter . McKay figures out that there is no way to guide the alternate reality drive , but that they can return to their original reality by reversing the drive and jumping back through the realities they had visited before . They use the maneuvering thrusters to stabilize the ship 's orbit above the red giant , and weather another attack by the aliens , with help from an alternate Atlantis . Once they return to their own reality , they leave the ship in space suits after a remaining alien detonates an explosive , causing a breach in the ship 's hull and are picked up by Lorne ( Kavan Smith ) after the Daedalus disappears . In the end , McKay is shown working on fixing the alternate reality drive , despite Sheppard 's admonishments . 
