In Mountaincrest, a stranger without memory arrives in a bar to have a drink. When he leaves the bar, a local tries to rob him but he turns into an animal and kills the attacker. Deputy Ben Clovey hunts down the animal but is wounded by it. Sheriff Jack Haines organizes a party to find the beast. Meanwhile the nurse Amy Standish and her father, the local doctor, receive a man called Duncan Marsh that recalls that he had a car accident and two doctors have treated him. But he flees and Haines wants to hunt him down but Amy and her father wants to convince him to capture Duncan to see how they could treat him. When is wife Mrs. Helen Marsh and her son Chris arrive in Mountaincrest, Sheriff Haines is convinced that shall capture the werewolf alive. But the doctors that conducted the experiment arrive in the town expecting to kill him. Written by Claudio Carvalho, Rio de Janeiro, Brazil