The Boy Who Cried Werewolf (1973)

Richie Bridgestone (whose parents are divorced) goes to spend the weekend with his father at his secluded mountain cabin. During a moonlight hike, they are attacked in the darkness by a creature that he recognizes as a werewolf. During the struggle, the werewolf falls into a ravine and is impaled by a wooden fence, but not before biting his father. Upon investigation, they find their attacker to be human and the sheriff concludes their attacker was an insane drifter. He spends the rest of the film trying to convince his mother, and his therapist that his father is now a werewolf.