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
Sir Joel Cadman
Herbert Rudley
Dr. Gordon Ramsay
Patricia Blair
Laurie Munroe
Akim Tamiroff
Odo the Gypsy
Phyllis Stanley
Daphne
Lon Chaney Jr.
Dr. Munroe, aka Mungo
Bela Lugosi
Casimir
John Carradine
Bohemund
