On a Swiss mountain, one of three student climbers is killed, his head ripped from his body. Two sisters, a London mind-reading act, are traveling by train to Geneva when one of them, Anne Pilgrim (Janet Munro), faints as they pass the same mountain. Upon waking, she knows that there is something very wrong, so she decides they should get off at the very next stop, Trollenberg.
The story centers on a group of researchers working in an underwater laboratory. After an encounter with an Unidentified Submerged Object (USO—an undersea flying saucer), the base is attacked by a monster that may be the vanguard for invading aliens. The researchers and the base's military staff must deal with the creature and destroy the USO.
Mad scientist Dr. Krellman attempts to cure his son's leukemia by doing heart transplant, replacing his son's heart with that of a gorilla's. The result of the operation transforms Krellman's son into a deformed and mutated man-ape hybrid taking on the characteristics of the organ's donor, who immediately goes on a bloody rampage.
After a whole eon, Kremmen has been awarded The Most Fabulous Man in the World Apart from God Award, and is presented with an enormous, fully automated spaceship shaped like a Brain. While Dr. Gitfinger examines the controls, Carla persuades Kremmen to have casual sex with her in their private quarters.