While based in the World War II time period, (TV: The Empty Child, The Doctor Dances) Captain Jack Harkness took the name and identity of an American airman he knew would die in battle on 21 January 1941. Jack hadn't known anything about the other Jack as a person, or even what he looked like until, transported from the 21st century to 1941 with Toshiko Sato, they met each other. In 1941 again, the future Jack adopted the name Captain James Harper. Distressed at the idea Nancy might actually be in love with him, he was unhappy about leading her on. (TV: Captain Jack Harkness)