Satan replaces the newly born son of a simple countryfolk couple with an evil imp of his making. By showing this creature parental love, Satan will be able to ascend to earth and rule. But things go not according to plan.
When crossing the equator for a first time aboard a ship, all passengers take part in a ceremonial dunking in the ship's swimming pool. One man refuses. He is visited by Neptune himself.
How Dr. Jonathan Weir comes into possession of the powerful artefact known as "The Purple Claw". His first opponent is fiendish Dr. Gool, who injects deceased people with his radioactive living fluid and forms an army of the undead.