Jay Felger, infamous for his failed projects, and Carter begin work on a computer virus designed to disable a DHD by scrambling its symbols and corresponding coordinates. But when Daniel, O'Neill and the other SG teams become stranded on other planets unable to dial home, Felger's Avenger virus seems to be doing something it wasn't designed to do: it's spreading. As the entire gate network shuts down, Felger and Carter look for a solution to repair the damage that was done.