A Canadian in London offers a safe hiding place to a British secret agent investigating a spy ring. However, when she is murdered, he realises he will be the prime suspect and goes on the run with the intention of exposing the real killers. Alfred Hitchcock's thriller based on John Buchan's novel, starring Robert Donat, Madeleine Carroll, Lucie Mannheim, Godfrey Tearle and Peggy Ashcroft