Directed by Freddie Francis* for Tigon, this film is a thrilling collaboration that pairs the iconic Christopher Lee and Peter Cushing. It’s a gem from the end of the era of British gothic horror, and despite its occasional silliness, such as Cushing holding a gigantic prehistoric finger that appears as sexualized as it gets, I find every moment of this film utterly captivating.

Cushing is Prof. Emmanuel Hildern, a scientist who discovers a colossal skeleton — Anunnaki alert — that is older than other skeletons in the area yet much more advanced. He hopes that this finding will win him the Richter Prize, but that award looks like it’s going to be won by his brother John (Lee), who has been looking after Emmanuel’s institutionalized wife for years. He plans to use his study of his brother’s wife to win that award and refuses to pay for the professor’s skeleton-finding trips.

Whatever this skeleton is, legend says that it was a monster that feared rain—maybe because the Great Flood wiped out the other Nephilim—and that it could grow skin when it came into contact with water.

Hildern has a theory that if evil itself—the skeleton—can be a living being, then it can be biologically contained and treated like a disease. He created a serum that can stop evil using cells from the skeleton’s fleshy finger. After testing the drug on a monkey with good results, Emmanuel also immunizes his daughter Penelope, who may have inherited her mother’s mental illness.

Of course, the next day, the monkey has gone wild, and now we have Penelope dancing on tables and slashing sailors. Soon, James finds out about the serum, kidnaps his niece and steals the skeleton. The skeleton gets exposed to the rain and becomes, well, a pretty goofy-looking monster that I can’t help but completely fall head over heels for.

The ending of this movie is a masterstroke, leaving the door wide open for interpretation. You can see it as Lee’s character denying that his brother is related to him to save his reputation or that Emmanuel was never a doctor at all but just another patient. If that’s true, then who really took his finger in revenge? Does the monster exist? It’s a thought-provoking conclusion that will keep you pondering long after the credits roll.

You can watch this on Tubi.

*Don Sharp, who also made Psychomania, was the original director before Francis was hired to replace him.