Alan Ladd plays Whispering Smith, a tough but soft-spoken railroad detective. His friend Murray Sinclair (Robert Preston), who has been fired from the railroad, begins aiding a group of criminals led by Barney Rebstock (Donald Crisp) in wreaking havoc on the trains, forcing Smith to go after him. There also appears to be a strong attraction between Smith and Murray's wife, Marian (Brenda Marshall).