Just when it looked safe to go back into the meadow, award-winning sheep Shaun is back with more hilarious farmyard antics and slapstick comedy, along with his frolicsome flock, the farmer and long-suffering sheepdog Bitzer. A cute mouse appears in the farmhouse and terrorises the farmer. Pidsley the cat is ordered to dispose of the rodent. When the mouse takes refuge in Shaun's fleece, the flock persuade him to protect their new friend from the pitiless cat.