Lord Bertie and Lady Libbie Mousley are the friendly mouse couple who live beneath the garden shed at Ruthmere, a beautiful home owned by Albert and Elizabeth Beardsley in the town of Elkhart. They love everything about Ruthmere, from its stunning art collection to its elegant dinner parties, and love to live as refinedly as the Beardsleys. One day, Mr. and Mrs. Beardsley’s dog, Fang, invites the Mousleys to a party. But when the hour arrives, Fang is nowhere to be found! The Mousleys must recruit help from their colorful cast of friends to seek out the missing pup.