 Starbug stumbles upon a battleship carrying on-board murderous cyborgs called "Simulants". When the "Simulants" infect Starbug with a virus and Starbug heads on a collision course with a volcanic planet. Lister, Cat and Rimmer connect Kryten to a Artifical Reality game set and Lister, Cat and Rimmer enters Kryten s dream of the wild-west, as they set out to help Kryten to fight the virus.