Donald Turner arrives home in Rochdale fresh from graduating as a fully qualified Veterinary Surgeon, and takes up a position with grumpy older vet Maurice Webb. He is horrified to learn that the Great Northern Zoo is a part of the practice, especially when he is called out on Maurice's day off to treat a chimpanzee who has had a thumb bitten off. The vet is needed so that they can say they 'Called In The Experts'.