In 1888, Jack the Ripper is on his killing spree. Scotland Yard Inspector O'Neill (Byrne) welcomes a visit from his old friend, New York City detective Sam Lowry (Patterson), who agrees to assist with the investigation. Sam becomes attracted to modern woman Anne Ford (McDowall) but her guardian, Dr. Tranter (Le Mesurier), doesn't approve. The police slowly close in on the killer as the public becomes more alarmed. The killer's identity is revealed and he meets a ghastly end.