 Two U.S. marshals, several street-level criminals, and a computer software pioneer (Donald Gelman) are all casualties of a bizarre diner shoot-out in the middle of the night. The Lone Gunmen help Mulder and Scully track down Invisigoth, a computer hacker who knew Gelman. She informs them about an artificial intelligence program created by Gelman that has deadly intentions. The only way to stop it is to feed it the "kill switch", a CD containing a neutralizing virus.