The Starbug crew travel back to Dallas in November 1963 and inadvertently change history causing an alternate reality to be created when Lister replaces Kryten's head with Spare Head 2 and they travel back through time so Lister can vindaloo when all the curry supplies aboard Starbug are destroyed in the aftermath of the battle with their future selves and Lister decides to set things right and restore history by getting President John F. Kennedy to assassinate himself.