When humble rancher Rick Patterson marries movie star Sabrina Eastman, his son Josh finds himself with a new step-sister, Lacey. The two kids do not get along and neither do their respective dogs: Josh's dog Meatball is a scruffy, farm mutt who's laid-back and friendly. Lacey dog Cassie is a prim, spoiled, purse city dog who is not into country living. Cassie and Meatball discover that a pair of bumbling crooks are plotting to steal Sabrina's prized possession - the valuable North Star diamond. Josh and Lacey discover that they are not as different as they imagined, and soon they realize something is definitely going on around their house. When Louie and Terrance kidnap the dogs and trick Josh and Lacey into going on a wild goose chase to find them, the crime is afoot. Meatball and Lacey escape their captors and must team up to prevent the two criminals from getting their hands on the diamond. It's dog versus man in a slapstick battle of wits. All leashes are off!