The Daedalus Variations

S5, E4: When a duplicate Daedalus zooms into orbit over the Atlantis, the crew investigates. Stepping aboard the dilapidated ship, they discover an ominous video message from its former captain and his words are far from reassuring. Before the team can get their heads around the increasingly sinister situation, the Daedalus doppelgänger hurtles into an alternate reality.