Villain(s)  Mad doctor

Actor(s):  Basil Rathbone, Akim Tamiroff, Lon Chaney Jr., John Carradine

Brief Description  The Black Sleep (1956) is an American black-and-white independent horror film directed by Reginald LeBorg and distributed by United Artists. Also known by its alternative title, Dr. Cadman's Secret, the film is celebrated among horror fans primarily for assembling an all-star ensemble cast of classic horror icons, including Basil Rathbone, Lon Chaney Jr., John Carradine, and Bela Lugosi in his final completed mainstream film role. Set in Victorian England in 1872, the gothic sci-fi narrative follows a brilliant but mad neurosurgeon who uses a death-simulating Eastern drug to harvest human subjects for radical brain-mapping experiments.

Plot:
The story opens in London, where a young, talented physician named Dr. Gordon Ramsay (Herbert Rudley) is falsely convicted of murder and sentenced to hang. On the eve of the execution, his former professor and legendary brain surgeon, Sir Joel Cadman (Basil Rathbone), visits him in his cell. Cadman offers Ramsay a way out by administering a mysterious, rare drug from India known as "Nind Andhera"—translated as "The Black Sleep". The potion induces a terrifying, death-like state of suspended animation, rendering the body completely helpless and cold, yet keeping the mind alive. Believed to be dead, Ramsay is wheeled out of the prison and taken to Cadman’s remote, dark countryside mansion—an ancient, repurposed abbey fitted with state-of-the-art neurosurgery labs, hidden doors, and a heavily locked dungeon cellar. Once Ramsay is revived, Cadman explains that he saved him so they can work together.

Cadman reveals his tragic motivation: his beloved wife, Angelina, is trapped in a deep coma caused by a brain tumor. He intends to map the exact functional zones of the human brain so he can safely operate on her. However, his methods are highly unorthodox and illegal. He relies on a sleazy gypsy named Odo (Akim Tamiroff) to supply him with fresh, living human "specimens" to operate on under the influence of the Black Sleep. As Ramsay begins to assist, he grows increasingly horrified by the reality of Cadman's work. Ramsay, along with Laurie Munro (Patricia Blake), the daughter of one of Cadman's missing subjects, stumbles upon the mansion's subterranean dungeon. There, they discover the terrifying side effects of Cadman's failed exploratory procedures. The cells are filled with a "monstrous gallery" of living human experiments who have been left severely mutated, physically disfigured, or driven violently insane due to brain damage.

When Ramsay confronts his mentor and refuses to cooperate any longer, Cadman traps both Ramsay and Laurie, intending to use them as his next surgical test subjects. Before Cadman can perform the surgeries, the imprisoned mutants in the cellar break free from their cells, led by the frenzied Mungo. The vengeful horde corners the mad doctor. As the mansion descends into chaos, Ramsay and Laurie manage to escape unscathed, while Cadman is overpowered by his own monstrous creations and falls to his death, putting an end to his horrific laboratory experiments. Released in June 1956 on a double feature bill alongside the sci-fi horror film The Creeping Unknown (also known as The Quatermass Xperiment), the movie was a major box-office success. It brought in over $1.6 million domestically against a very modest production budget.