The crew have survived their battle with their future selves. If the future crew had killed their former selves, they would have eliminated their own existence, and therefore not have been able to destroy themselves. (See temporal paradox.) Unfortunately disaster has struck - Starbug is completely devoid of Indian food supplies--no curries, not even a poppadom. Lister (Craig Charles) proposes that they go back in time to an Indian take-away and order 500 curries. Rimmer (Chris Barrie), Cat (Danny John-Jules) and Kryten (Robert Llewellyn) are against the idea and oppose going back in time because they want to avoid the timeline in which their future selves try to kill their former selves. However, Lister removes a guilt chip from one of Kryten's spare heads and swaps them, telling the new guilt-less Kryten to reassure the crew that it will be okay. The crew assents and they travel back in time.
Their time-travel calculations are a little off and they find themselves in Dallas, Texas on November 22, 1963. They appear at the Texas School Book Depository just as Lee Harvey Oswald is taking aim at U.S. President John F. Kennedy. They knock him out the window where he dies by hitting the ground, preventing Kennedy's assassination. Police arrive and attempt to arrest the crew for the murder of Oswald as well as the attempted murder of the president. However, the crew escapes by using the time travel device to travel three years forward to 1966.
Kennedy's survival causes an alternate timeline where he has been impeached and removed from office (due to sex scandals) and the new president, J. Edgar Hoover, is controlled by the Mafia. The USSR is allowed to install a nuclear base in Cuba in return for Mafia cocaine trafficking between Cuba and the States. With a Soviet nuclear base 30 miles from the US mainland, people flee from all the major cities. The crew attempt to correct the situation by returning to the day of the shooting and driving Oswald to a higher floor in the building, but this plan still fails to lead to Kennedy's death. Lister travels to Idlewild Airport in 1965 and persuades a post-impeachment Kennedy to travel back to 1963, become a "second gunman" on the grassy knoll, and shoot himself. The plan works: Kennedy shoots his past-self and the timeline is restored. Kennedy thanks the gang for the chance to save history, and fades away as a result of the resetting timeline. Lister, too late, realizes he forgot to ask Kennedy for the name of a good Indian take-away, and suggests that they use the time drive to start the search for Indian food all over again. The other members of the crew begin beating and kicking Lister to prevent him from using the time travel device.