Their time travel calculations are a little off and they find themselves in Dallas, Texas on 22 November 1963. They appear at the Texas School Book Depository just as Lee Harvey Oswald is firing at U.S. President John F. Kennedy. Having inadvertently knocked him out the window onto the window ledge, they accidentally cause Oswald to fall to his death below when he tries to re-enter the Depository, thereby preventing Kennedy's assassination. Confronted by the local police who believe that they are part of Oswald's assassination attempt, the crew use the time travel device to go three years forward to 1966.