In 19th century England, a noted brain surgeon rescues a former student from being hanged on a false conviction for murder, and spirits him away to an ancient, repurposed abbey far in the countryside. There, he connives his pupil into assisting him in mapping the functions of the various parts of the human brain, using living subjects who are under a terrible animation-suspending drug called "black sleep". Subsequently, the student, along with the daughter of one of the subjects, discover that most of these subjects have survived but are being kept in a dungeon-like cellar, in various stages of physical and mental derangement...
Basil Rathbone
as Sir Joel Cadman
Herbert Rudley
as Dr. Gordon Ramsay
Patricia Blair
as Laurie Munroe
Akim Tamiroff
as Odo the Gypsy
Phyllis Stanley
as Daphne
Lon Chaney Jr.
as Dr. Munroe, aka Mungo
Bela Lugosi
as Casimir
John Carradine
as Bohemund
George Sawaya
as Sailor-Subject
Tor Johnson
as Mr. Curry
Sally Yarnell
as Female Subject
Peter Gordon
as Sgt. Steele
