One of the Athosian children unwittingly unleashes a seemingly harmless entity, the team gets trapped while fleeing from the Wraith, and Dr Weir suspects there is a spy in the group.
Colonel Caldwell (Mitch Pileggi) saves Major Sheppard (Joe Flanigan) from his suicide run on the Wraith ships, the battle cruiser Daedalus becomes infected with a virus that may allow the Wraith to take over the ship, and Teyla (Rachel Luttrell) and Sheppard are taken captive by a former soldier.
Dr McKay and Ronon (Jason Momoa) are captured by Wraith hive ships, the Atlantis team sets up a PoW camp for former Wraiths, and Dr Beckett (Paul McGillion) falls under the influence of a mysterious stranger.
The expedition is left with 24 hours of power after the hyperdrive shuts down, Sheppard plans to steal a power source from the Replicators, and the team stumbles upon survivors from Ronon's homeworld.
Carter races to save the trapped crew members from the rubble of the facility, Dr Jennifer Keller (Jewel Staite) develops a mystery illness, and Ronon is captured by former ally Tyre (Mark Dacascos).