Synopsis by Rovi
In a mountain home, Dr. Cliff Groves (Robert Shayne) is working hard on the theories that have driven him to the point of overbearing obsession, frightening his sister Jan (Joyce Terry), who lives with him. When the local game warden is shocked to see what looks like a saber-tooth tiger in the area, he consults scientist Dr. Ross Harkness (Richard Crane) about the mysterious animal, and the two men decide to find the tiger and kill it. Meanwhile, Groves' experimentation has escalated. One night he injects himself and turns into a savage Neanderthal man who commits a murder and a rape then quickly returns home and transforms back into Groves. When Dr. Harkness finds evidence to incriminate Groves, he confronts the madman, who transforms again, kidnapping a woman and fleeing into the woods. Unfortunately for Groves, a second saber-tooth tiger, created by injecting a housecat with his own formula, tears him to pieces; transforming back to himself, he murmurs "It's better this way," as he dies. This wearily routine variation on Dr. Jekyll and Mr. Hyde was directed by E.A. Dupont, who once had a substantial reputation, based on his film Variety; his work here is indistinguishable from that of any standard low-budget hack. However, the dialogue by producers Aubrey Wisberg and Jack Pollexfen is, if nothing else, highly identifiable -- they wrote some of the most ponderous, hard-to-say lines in movie history. "All I can say," poor Robert Shayne has to say, "is that I cannot determine now which I admire less in you, your humor or your wit." The makeup transformations are weirdly elaborate, though the end result -- the Neanderthal Man himself -- is rendered by a standard rubber mask. The script is not only badly written, it's clumsily organized, with way too much time spent on the saber-tooth tiger, and very little, relatively speaking, on the menace of the title. Intrigued, Ross heads up to the town, and meets Ruth Marshall (Dorris Merrick), Groves' fiancee, who has him drive her to the Groves home. Groves himself becomes furious when a group of Los Angeles scientists refuse to believe his theory that Neanderthal Man had a larger brain than human beings today. He stays furious when he meets Harkness, and when the game warden and Ross kill the saber-tooth tiger, he's initially still angry -- but is in a better mood when the body proves to have vanished.
America, cat, caveman, creature, evolution, experiment, housekeeper, injection, mad-scientist, mild-mannered, monster, Neanderthal, scientist, serum, tiger, transformation, wild [undomesticated], director