Mysterious Intruder is a 1946 American mystery film noir based on the radio drama The Whistler. Directed by William Castle, the production features Richard Dix, Barton MacLane and Nina Vale. It is the fifth of Columbia Pictures' eight "Whistler" films produced in the 1940s, the first seven starring Dix.

Plot

Edward Stillwell, the aged proprietor of a music store, hires private detective Don Gale (Dix) to find Elora Lund, who, after her mother died seven years before, vanished at the age of fourteen. Stillwell can only pay $100, but hints mysteriously that finding Lund could make Gale a rich man.