The “Dad’s Army” takes us to Walminton-on-Sea in World War II, which is about to end. The National Guard has not had much participation in the fight, since it has developed far from England, so that its members do not have the very high moral.
One of its members is Captain Mainwaring, who also commands a platoon that has not been fit to fight, so if shame is double. His morale is on the ground, but something happens that will make it rise.
MI5, the British interior secret service, has discovered that a radio signal comes from Walmington-on-Sea, a signal that is almost certainly a spy.
That will give the National Guard a chance to redeem itself in the contest, since it will finally be able to render a good service to his country, capturing the spy that is informing the Nazis.