Synopsis

Two U.S. college students (David Naughton and Griffin Dunne) are backpacking on the British moors when they are attacked by wolves. Dunne's character is instantly killed, but Naughton's character is only severely injured. Dunne's corpse comes and visits him while he's in the hospital and warns him to kill himself by the full moon, or he's doomed to turn into a werewolf. Naughton naturally doesn't believe this. He goes on living and even finds romance with his pretty young nurse (Jenny Agutter).

Naughton is in his London house during the night of the full moon, and it happens: he gets fangs, a snout, a ferocious face, and a hairy body. Then he goes out and kills some London residents who happen to be out at night. When he wakes up in the morning, he's naked and sleeping in a cage at the zoo.

He soon discovers that Dunne was right and realizes the awful truth: he is the one responsible for the deaths that occurred the night before. He is haunted by visions of his victims, and Dunne appears again, telling him that he has to commit suicide before he turns into a werewolf again. He doesn't kill himself, though, and once again he turns into a wolf, and look out London again. Finally the police shoot him as a wolf, but he turns back into a human when he dies.