Cujo, a friendly St. Bernard, chases a wild rabbit and inserts his head into a cave, where a rabid bat bites him on the nose. The Trenton family—advertising executive Vic, housewife Donna, and young son Tad—take their car to the rural home of abusive mechanic Joe Camber for repairs, where they meet Cujo, the Camber family's pet, and get along well with him.