A new Stargate team embarks on a dangerous mission to a distant galaxy, where they discover a mythical lost city -- and a deadly new enemy.

Sheppard tries to convince Weir to mount a rescue mission to free Colonel Sumner, Teyla, and the others captured by the Wraith.

The Atlantis base is threatened when the team discovers that an alien entity is in the city. McKay's experiment with alien technology goes awry.

The team finds themselves in mortal danger when their Puddle Jumper ship becomes lodged in the Stargate.

After a series of run-ins with the Wraith, the team begins to suspect their Athosian allies of having a spy in their midst.

With a group of Wraith hive ships on the way to Atlantis, the team searches for a place to flee and a way to destroy the city. McKay leads a team to try and activate the Ancients' orbital weapons platform.