A team of scientists think they have found the location of the long lost city of Atlantis. It can be reached by a Stargate address that leads to the Pegasus galaxy.
Rodney can't remove an Ancient device that makes him invincible but prevents him from eating or drinking. Meanwhile, there are power malfunctions throughout the city and one of the Athosians mentions seeing a shadow.
Sheppard gets bitten by a Wraith-like bug and is dying. While the puddle jumper returns, it gets stuck in the Stargate. There's 38 minutes to find a solution.
Atlantis wants to trade food with the Genii, a simple civilization who turn out to be not so simple. They are planning a nuclear attack against the Wraith.