Jones' butcher van is converted into an armoured car for the platoon.

The Platoon spend the weekend at a training facility, where they are challenged to capture an officer.

Mainwaring gives the platoon a lecture in communications but when a German plane crashes into the town's reservoir it becomes obvious that many of the men have no idea how to use a telephone and, when Mainwaring gets through to the main exchange to notify the incident, the operator is no help. Whilst a guards officer attempts to take command of the situation from Mainwaring, Walker saves the day by getting the reservoir manager to open the sluices, forcing the Germans to swim for it.

Mainwaring is extremely annoyed that all the platoon - except Godfrey, who was too slow - have used up all their ammunition firing in vain at a low-flying German aeroplane. An inquiry is ordered - along with a new case of ammunition, which duly arrives. The captain in charge of the inquiry, which takes place in the church hall in competition with choir practice, feels it a waste of his time but talks the men through what happened. Jones says he gave the order to shoot. Mainwaring corrects him by saying 'Fire', which the platoon does, making a hole in the roof.

Mainwaring and Wilson are trapped in the bank with an unexploded bomb.

Mainwaring discovers that he was never actually promoted to Captain, and must adjust to life at his correct rank: Private.

A large field gun has been delivered to the church hall for a demonstration by the platoon but none of them know how it works. After a process of trial and error using models to represent the town, the time comes for the gun to be fired but the men get tangled up in the netting enclosing it.

After Mainwaring complains that the men's saluting is sloppy a runaway barrage balloon appears with the verger clinging onto it. He is rescued and various people, including Godfrey's sister Cissie, are asked to hang onto it until Mainwaring takes charge. Unfortunately for him it takes off in the breeze with him holding onto the other end of its rope, dragging him through trees and a haystack until it stops on a railway bridge. The men are about to secure it but then an officer comes by and in order to perfect the saluting so beloved of Mainwaring they have to let go of the balloon.. .

Pike's work is suffering because he is distracted by his girl-friend Violet, whom Mainwaring regards as common as her mother used to clean for him. Furthermore at the upcoming platoon dance Pike is going to announce his engagement to her, which alarms Wilson as Mavis would never let her baby go. Mainwaring arrives at the dance with a black eye after a fight with his wife and, despite efforts by Jones - doing impressions - to stall Pike, the lad announces his big news. Mavis faints. Later she locks Wilson out of the house for not telling her of her son's plans and he joins Mainwaring, also shut out by his wife, in the church hall. Pike declares the engagement off after Mavis has thrown a bucket of water over him.

Mainwaring and his platoon get into a pickle when they're put in charge manning an observation post on a derelict pier.

It is revealed that Private Godfrey was a Conscientious Objector in the First World War, leading Mainwaring and some of the platoon to brand him as a coward. However, during an exercise in which Mainwaring collapses with smoke inhalation, it is Godfrey who, at risk to himself, rescues him. When Mainwaring and the others go to visit Godfrey, recovering in bed, they see a photo of him with a military medal, won in the First World War when he was a brave stretcher bearer who saved many lives. Mainwaring is ashamed and asks Godfrey to be the platoon's official First Aid representative.

Walker has found a discarded parachute which he cut up to make ladies' knickers. This leads to an embarrassing examination of the ladies' pants to determine their colour as British parachutes are white and Germans are cream. Using a tracker dog the platoon go into the woods where they trap a man with a foreign accent - but he is an Austrian bird-watcher hunting the rare golden oriole. Eventually a German parachutist appears, asking to be arrested.

Pte. Fraser loses the butterfly spring from the platoon's Lewis gun, and fears it is trapped inside a coffin with the late Mr. Blewitt.

The platoon buys a canoe, and intends to create a river-based defense system, but get lost and drift into the ocean.