The Daedalus arrives to defend Atlantis from the Wraith onslaught, but it may not be enough when the team discovers that an even larger armada is on the way.

The Daedalus is infected by a Wraith computer virus, while members of the expedition hope to return to Earth.

Sheppard and his team attempt to locate Lieutenant Ford, only to find themselves captives of a former soldier who is being hunted by the Wraith.

A run-in with a Wraith Dart leaves the consciousness of a precocious Atlantis security officer trapped in Dr. McKay's mind.

The Atlantis team finds a culture that lives in relative safety from the Wraith, because they hand over their criminals to the Wraith -- and crash-land in the volatile penal colony.

McKay puts the team at risk when he tries to perfect unfinished Ancient technology that wiped out a civilization. Ronon Dex discovers that he is not the lone survivor from his world.

Colonel Sheppard begins to undergo a disturbing physical transformation after being exposed to Beckett's anti-Wraith drug.