 McKay, Zelenka and Ford and a team of scientists are inspecting a section of the city flooded during the storm, but everything appears to be just fine. When they plan to return, two team members are missing. Over the radio they seem to be frightened by something and are found dead. The team suspects a virus and a city-wide quarantine is set in place. Then one of the other team members collapses. A scientist named Peterson is frightened by the prospect and manages to escape, risking infection to the entire city. Sheppard is forced to defy Weir s orders and goes after him with Teyla. Meanwhile the infected team discovers a viral lab. It is soon found out the virus causes hallucinations and certain death by forming an aneurysm. McKay realizes he is one of the next to go.