Dr. Morgan and Dr. Cavigny star as a brace of scientists who return from the West Indies with a potent, phosphorescent serum that allegedly changes human beings into cats.
On the beach one night, Christine Faber, two years a widow, thinks she hears her late husband Paul calling out of the surf...then meets a tall dark man, Alexis, who seems to know all about such things. After more ghostly manifestations, Christine and younger sister Janet become enmeshed in the eerie artifices of Alexis; but he in turn finds himself manipulated into deeper deviltry than he had in mind...
During the War, a British agent travels to the remote Glennye Castle in the wilds of Scotland to investigate a mysterious murder by a masked phantom. Who or what is the phantom? And how are the Germans involved?
A woman is married to the son of a doctor, the proprietor of a private sanatorium, where she is under unwilling treatment. Both the son and the doctor indicate they want the marriage dissolved. Arriving at the scene is a mysterious personage identified as the doctor's cousin who formerly was a stage magician in Europe. He is accompanied by a threatening dwarf.
Tod Slaughter goes about the countryside strangling everybody. His evil scheme is to destroy the family who wronged him. He has a secret lab complete with a torture chamber, featured in the films climax. Probably the most maniacal portrayal Tod ever gave.
A schooner disappears at sea without a trace. Years later, evidence of possible survivors prompts the mother of the schooner's mate Jose to hire a tuna boat to investigate. They discover the lad living happily on a South Seas island, and, when he refuses to leave with them, they abduct him. However, Jose gets revenge by leading the ship into the lair of a mysterious giant manta ray.
A demented archaeologist discovers a living, breathing serpent creature known to the Aztecs as Quetzalcoatl and accidentally kills his wife by giving her one of the beast's feathers, causing the creature to track her down and slaughter her. Using this knowledge he exacts revenge upon his enemies by placing one of the feathers on his intended victim and letting the beast loose to wreak havoc.
The bell ringer at a way station in the French Alps, murders a passing horse trader with a thrown rock and relieves him of his bankroll, in order to bribe the daughter of his only friend, a head injury victim considered the village simpleton, into marrying him, despite her love for a lowly woodsman who is, in turn, being cajoled into marriage by the daughter of the wealthy innkeeper.
Suspecting that a safari guide is a wanted killer, undercover policeman Geoffrey Bishop (Richard Fraser) joins a safari led by the suspect for a scientist that hopes to find and prove that a fabled white gorilla is a missing link.
Leo, a former convict, is living in seclusion on an island with his step-daughter, the daughter of his late wife. Leo was framed by a group of former business associates, and he also suspects that one of them killed his wife. He has invited the group to his island, tempting them by hinting about a hidden fortune, and he has installed a number of traps and secret passages in his home. He is aided in his efforts by a former cell-mate who holds a grudge against the same persons. When everyone arrives, the atmosphere of mutual suspicion and the thick fog that covers the island promise a tense and hazardous weekend for everyone.