In this tale of vengeance, Bruce is a young teenager who is the leader of the Liu City gang, who gets into trouble and street fights every now and again.
A little girl is left by her father in an exclusive seminary for girls, due to her father having to go to South Africa to fight in the Second Boer War.
Dr. Cameron (George Zucco) has succeeded in his experiments with a serum which will turn a man into a wolf-like monster and is ready to avenge himself on the men who caused his professional failure. He uses it on his gardener Petro (Glenn Strange) and one after the other is killed by his creation...
Ellen has been taking care of her insane younger sister Cissy ever since their explorer father died. When Cissy's pet ape dies in their mansion's dungeon and Ellen finds a boyfriend, Cissy's incestuous desire for her sister turns deadly.
