70s after school movie snake bite faked with stapler

Little Richie Bridgestone goes to spend the weekend with his father at his secluded mountain cabin, and witnesses his father being attacked by 'a creature' that the boy recognizes as a werewolf. He tries to convince his mother and his therapist that his father is now a werewolf.

A Californian family inherits a castle in Romania. This is especially exciting to the son, who is obsessed with monsters. And he is not disappointed.