Britain is facing invasion by Hitler and his Nazi hordes - and the men of the Walmington-on-Sea Home Guard are facing a crisis of their own. Private Walker, source of their supplies of whisky, cigarettes and other essential black market goods, has been called up to the army. Captain Mainwaring decides to use all his standing as an officer and a bank manager to have Walker excused from military service. Meanwhile, Jones and co try to ensure that Walker fails his army medical. (Gold recreates three episodes of Dad's Army that haven't been seen on television since they were first broadcast in 1969.)