The kids let Marmaduke outside to greet their father Mr. Winslow as he gets home from work. Once inside there is a knock at the door. It's the police and a member of the lost pet society who claims that Marmaduke is actually the lost dog of Mrs. Van Upton named Hobart. They two men haul off Marmaduke upsetting the entire Winslow family. The kids follow Marmaduke in an effort to get him back.