University professor George Kingsley is struck by gangsters while crossing the street, leaving him with brain damage and one of the gangsters, Cannon, paralyzed. Kingsley's friend Dr. Sovac attends to both men, and when Cannon offers him a reward for aiding his recovery, Kovac transplants part of Cannon's brain into the dying Kingsley's skull, creating a dual personality.
A fugitive, dangerous madman reaches an English village where he confronts his former partner who left him for dead in the jungle after their discovery of a diamond mine. When the former partner also claims to have since lost the mine and all its wealth, which he took all for himself, and though the partmer is still living in a state of luxury , the madman takes up an offer from a crazed scientist to make him invisible, something the scientist has already done with experimental animals, so that he can take revenge.
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...
Following his forced retirement from an appalling rock band, Jason decides to vacation at Brittlehouse Manor, a health farm run by the leather-gloved, ex-Nazi scientist Dr. Storm. Along the way, Jason meets Judy, also on her way to Brittlehouse Manor to visit her aunt, who married Dr. Storm some years ago. Once they arrive, the pair realise rather quickly that something is wrong, probably because the other guests have had their brains surgically removed, or all the blood pouring from the sink, or possibly just because the creepy midget keeps telling them to brush their teeth.
A scientist working on cures for rare afflictions, such as a bone softening agent made from molds to allow him to correct the spinal deformity of his nurse, finds the physical causes of lycanthropy in wolf-man Larry Talbot and of vampirism in Count Dracula, but himself becomes afflicted with homicidal madness while exchanging blood with Dracula.
After Malukan immigrants engage in a string of corpse mutilations at various New York City hospitals, a doctor and a morgue assistant travel to the Maluku Islands to investigate.
A mad doctor uses a fake taxi driver to kidnap victims and then removes their eyes in hopes of perfecting an eye transplant that will allow his blind wife to see again. One of the doctor's servants ends up getting possessed by not one, but several of the victims.
The eminent Dr. Phibes awakens from a decade of suspended animation and heads to Egypt with the corpse of his dead wife, which he intends to resurrect by murdering people in strange and heinous ways.
A brilliant but deranged neurosurgeon becomes obsessively fixated on a judge's daughter. With the help of an escaped criminal whose face he has surgically deformed, the mad man lures her, her father, and her fiancé to his isolated castle-like home, where he has created a torture chamber with the intent of torturing them for having 'tortured' him.
After a team of surgeons botches his beloved wife's operation, the distraught Dr. Phibes unleashes a score of Old-Testament atrocities on his enemies.
Dr. Leon Kravaal develops a potential cure for cancer, which involves freezing the patient. But an experiment goes awry when authorities believe Kravaal has killed a patient. Kravaal freezes the officials, along with himself. Years later, they are discovered and revived in hopes that Kravaal can indeed complete his cure. But human greed and weakness compound to disrupt the project.