Nick and Sally are trying out their new blue rubber boots but they keep getting stuck in the mud! The Cat knows just who can help them-Buster, the blue-footed booby bird. Buster is only too happy to show them how his wide, flat blue feet help him move easily over the muddy shore. The Cat helps to make their boots wide and flat, and now Sally and Nick can walk across the mud without getting stuck-just like Buster!