The Black Sleep is a 1956 American Black-and-white horror film scripted by John C. Higgins from a story by Gerald Drayson Adams developed for producer Aubrey Schenck and Howard W. Koch who had a four-picture finance-for-distribution arrangement with United Artists.
The film was released in 1956 on a double bill with the British sci-fi film The Creeping Unknown. The Black Sleep was later re-released in 1962 under the title Dr. Cadman's Secret.
Set in England 1872 the story concerned a prominent kinghied surgeon whose wife has fallen into a coma caused by a deep-seated brain tumor Due to medicine's stare of the art at the time he does not know how to reach the tumor without risking brain damage or death to the woman he loves so he undertakes to secretly experment on the brains of living but involuntary human subjects who are under the influence of a influence of a powerful Indian anesthetic Nind Andhera which he he calls the "The Black Sleep" Once he has finished his experimente subjects are revived and placed in seriously degenerated and mutilated states in a hidden cellar in the gloomy abandoned country abbey where he conducts his expermente.
- Basil Rathbone as Sir Joel Cadman
- Akim Tamiroff as Udu the Gypsy
- Lon Chaney Jr. as Dr. Moroe aka Mungo
- John Carradine as "Bohemund"
- Bela Lugosi as Casimir
- Herbert Rudley as Dr. Gordon Ramsay
- Patrícia Blair as Laurie Muncoe
- Phyllis Stanley as Daphnae
- Tor Johnson as Curry
- George Sawaya as Sailor Subject
- Sally Yarnell as Female Subject
- Peter Gordon as Det.Sgt. Steele
- Claire Carleton as Camoda Daily
- John Sheffield as Det. Redford
- Clive Morgan as Rounsman Blevins
- Louanna Gardner as Angelia Cadman
- Aubrey Schenck as Prison Coroner's Aide (uncredited)
Sir Joel Cadman a mad scientist kidnaps his victims and cuts open their brains in an effort to discover a means to cure his wife's brain tumor.