They Met in the Dark (also known as Dark End and Spionagering M ) is a 1943 British comedy thriller film directed by Karel Lamač and starring James Mason, Joyce Howard and Edward Rigby. The screenplay concerns a cashiered Royal Naval officer and a young woman who join forces to solve a murder and hunt down a German spy ring. The film features a single song sung by Phyllis Stanley, "Toddle Along" (Ben Frankel, Moira Heath). The film is very loosely based on the 1941 novel The Vanishing Corpse by Anthony Gilbert.