In this animated adventure, chipmunk Alvin has werewolves on his mind. After being haunted by a creepy nightmare, he is convinced that his eerie next-door neighbor, Mr. Talbot, has a monstrous secret. As he and his brother Simon investigate, shy sibling Theodore, who has been reluctantly cast in the school's production of "Dr. Jekyll and Mr. Hyde," finds his inner monster after being attacked by a strange dog.