Plot summary

The picture opens with narration over a black screen. Basil Rathbone tells us, "The ancients who wrote in the sensory tongue made first mention of the strange drug they called Nind Andhera. This drug was first introduced into the city of Lahore in the Punjab in the 703rd year after the death of the Prophet, praise his memory. This drug has the power to place a mans body and limbs into helplessness and his soul sleeps. Nor does he feel pain. He is as a dead man, yet he is not of the dead." Title and credits follow.A wide shot of Newgate Prison in London in the year 1872 is followed by two guards and Sir Joel Cadman (Basil Rathbone) going to see a prisoner. Dr. Gordon Angus Ramsay (Herbert Rudley) is a condemned man, scheduled to hang the next morning. Cadman was his medical school teacher. Ramsay is chained to the wall. He complains that he was convicted on circumstantial evidence of killing a man named Curry. Ramsay does admit to some of the facts, but does not remember most of what occurred. Most distressing to Ramsay is the fact that after being hanged his body is to be delivered to a medical school for dissection, instead of a proper burial. Cadman assures his student that will not happen. He has interceded with the Lord Chief Justice to get that provision of his sentence rescinded. Cadman is to get Ramsay's body and will be buried properly. Cadman pops the top on his walking stick and pours a small amount of powder into a cup. He instructs Ramsay to take a drink in the morning before the guards come for him. He explains it is only a sedative to help him cope with the ordeal. The next morning in his cell, while the crowd outside gets restless, three men stand next to the dead body of Ramsay. The prison doctor pronounces time of death at approximately 5:00 a.m.Odo the Gypsy (Akim Tamiroff) escorts Dr. Cadman to a room containing a coffin containing the body of Dr. Ramsay. Cadman prepares a syringe and inject the antidote into the arm of Ramsay, which shows signs of rigor mortis. Cadman and Odo hold the body down. Ramsay begins to revive, his body racked with spasms and labored breathing. Cadman informs his student, "You're dead Dr. Ramsay." He then reads the Death Certificate to Ramsay. Odo and Cadman lift Ramsay out of the coffin. Cadman reveals that the antidote must be administered within twelve hours or death occurs, and his reason for the rescue from the hangman. Cadman objects to state sponsored murder and that he needs the help of a skilled surgeon. Ramsay voices his appreciation.At St. Griffins, an old abbey on the east coast of England, Cadman and Ramsay arrive by carriage. Casimir (Bela Lugosi) answers the door and takes their hats and coats. An immediate commotion ensues. Laurie Monroe (Patricia Blair as Patricia Blake) runs screaming to Dr. Cadman followed her tormentor, Mungo (Lon Chaney) formerly Dr. Monroe. Mungo approaches dragging one foot and is unresponsive to Dr. Cadman's orders to stop. Mungo pushes aside the two medical men and attacks Laurie. Daphne (Phyllis Stanley), Cadman's nurse appears. She is the only person who has any influence over Mungo. Mungo releases Laurie and takes Daphne's hand then limps away. Cadman escorts Ramsay to his room. Daphne tends to the comatose body of Cadman's wife, Angelina (an uncredited Louanna Gardner). She brushes her hair and takes her temperature. Cadman enters and is briefed on his wife's condition. Cadman tells his nurse he must operate soon. He plans brain surgery to cure the paralysis and coma.The next morning the two medical men have breakfast and discuss the Mungo mishap. Ramsay thinks Mungo looks familiar and is informed that Mungo was a lecturer at the medical college, Dr. Monroe. He suffered a brain disease and Cadman promises to cure him. Cadman then shows Ramsay a diagram of the brain and explains the areas and their functions. The full nature of Ramsay's task is explained, "The work is too complex for one man. You, doctor, you shall help me complete my chart." Cadman leads Ramsay through a door at the back of a large, open, fireplace. The secret door leads to an old part of the abbey tower Cadman now uses for his surgery. Daphne and Laurie are already present and preparing a cadaver for surgery. Cadman and Ramsay wash their hands while Daphne finishes shaving the head of K6, a sailor (George Sawaya). Ramsay is under the impression that the sailor is a cadaver, but will soon learn to the contrary. Cadman marks the skull for surgery then begins. He opens a section of the skull and applies electrodes to parts of the exposed brain. The body responds by lifting his right arm, next by trying to speak, and finally by opening his eyes. Cadman cuts a section of brain away which results in the leakage of cerebral fluid. Ramsay now realizes the cadaver is actually a heavily sedated man. Cadman explains that K6 is under influence of Black Sleep and feels nothing. Ramsay is shocked and horrified and expresses his surprise at the callous disregard for human life Cadman shows.Ramsay is in his room when he hears a knock at the door. A note is shoved under the door. He hears Laurie scream in the hall and goes to investigate. Mungo is attacking the woman. Ramsay tries to help and is attacked by Mungo. Daphne appears from her room and saves Ramsay. Returning to his room, Ramsay reads the note and heads for the kitchen. He hides when Casimir appears carrying a bed warmer. In the kitchen, he meets with Laurie. Laurie explains that Mungo is Dr. Monroe, her father. Casimir interrupts the couple to get coals for the bed warmer. Ramsay comforts Laurie, he explains that Cadman will help and operate on her father. Laurie informs Ramsay that Cadman has already operated. Prior to surgery Dr. Monroe was paralyzed on one side of his body, but otherwise normal and kindly towards her, but after surgery the paralysis was cured, except for the foot dragging, but his personality was completely changed. Laurie tells Ramsay there have been other surgeries but she does not know where the bodies have gone.The next morning Ramsay is finishing his notes on the previous surgery. Cadman expresses his appreciation to have a colleague and trained man to assist in the work. Cadman reviews the notes. Ramsay asks Cadman about the surgery on Dr. Monroe. Cadman finally admits that he damaged the reasoning section of his brain. He also admits the sailor is recovering, but there have been changes. Odo makes a call on Cadman to inform him that he is having trouble obtaining another surgical candidate--a woman, the mistress of Curry. Ramsay is tormented by his work and sleeps fitfully.In London, a woman calls on Odo at his studio. Carmona Daly (Claire Carleton) has come in regards to some work. Odo explains that he is in need of a model, but she expresses reluctance to prostitute herself. Odo assures her that he only wishes to sketch her face. He drugs her, but before he can make transportation arrangements the police pay a call on the studio. Sgt. Steele (an uncredited Peter Gordon) and Roundsman Blevins (an uncredited Clive Morgan) search the studio, with Odo's permission. They are looking for Miss Daly in regards to the Curry murder case. She had provided some information and is needed for further questioning. Odo decides not to revive Carmona Daly and disposes of the antidote.At the abbey, Cadman informs Ramsay that a final experiment, a dual surgery, is to be performed the next day. Ramsay asks Laurie where the post-surgical recovery area is located. She tells Ramsay she does not know. He asks about Curry, but she tells him names are never used, but, "Dr. Cadman pointed at the big man and said Curry powder comes from India and so does the black sleep, they ought to hit it off." Ramsay confides his secret and explains he needs to find Curry and alive to free himself. They walk behind the fireplace, but open the wrong door. That passage takes them down into the basement, instead of up to the tower and the surgery. Ramsay opens a locked door and the pair explore. This basement room is the recovery area. They first encounter a very thin man with very long hair. He is named Borg (John Carradine), but he calls himself Bohemond, a crusader. He rambles about the Holy Land. They walk on and find the sailor identified as K6. His face is contorted, one eye closed and skin lesions covering the right side of his face. He begs for help, then tries to kill Dr. Ramsay. Their third discovery is a woman, young Nancy (Sally Yarnell), who laughs maniacally. She is covered in patches of tufts of hair all over her arms and back. Finally, Laurie and Ramsay find Curry (Tor Johnson). Like all the others he is chained to the wall. Curry is now bald, blind and mute. Cadman, Mungo, Daphne and Casimir appear. Ramsay and Laurie are taken out of the basement by force. Curry finds the keys to the chains that Ramsay dropped in his niche. Cadman accuses Ramsay, "You've been very foolish Dr. Ramsay. Foolish and very ungrateful. I saved your life." Ramsay demands to be allowed to leave. Cadman refuses. Odo arrives with the dead body of Carmona Daly. Odo suggests Laurie substitute for Miss Daly and Cadman agrees. He will use her during the operation on his wife to avoid sensitive areas of her brain. The police arrive and Casimir is sent to delay their interference. Sgt. Steele presents himself along with Det. Redford (an uncredited John Sheffield) to Cadman. They inquire as to the location of Carmona and Odo, then depart the abbey after Cadman satisfies their questions. Cadman goes to retrieve his wife while Ramsay tries to escape with the now sedated Laurie. He decides to drug Mungo and carry Laurie out. Daphne is attacked behind the fireplace by Borg and the other three basement escapees. Daphne catches fire and runs away. The former surgical patients go up to the surgery. Ramsay administers the antidote to Laurie. Mungo recovers from his anesthesia as Laurie recovers from the Black Sleep. The four former patients enter the surgery and attack Mungo. They dispatch Mungo then turn their attention on Cadman, who arrives with his wife in his arms. Laurie and Ramsay slip past the crowd and escape the room. Cadman is not so lucky. He is chased out of the room and fall off the stairs (no guardrails, remember this is a 10th century abbey). The police are there to greet the pair as they exit the fireplace door. Odo is placed under arrest and taken away. We close with Laurie and Ramsay walking arm in arm away from the abbey.