British intelligence fakes the death of Edgar Brodie (John Gielgud) to send him on a mission in Switzerland, where as Richard Ashendon he is to locate and kill a Germany spy. Accompanying Brodie are fellow agents Elsa Carrington (Peter Lorre), who is to play Brodie's wife, and an eccentric assassin known as The General (Madeleine Carroll). Locating the spy on a train, Brodie and Elsa have second thoughts about their mission just as an American (Robert Young) ingratiates himself with them.