The platoon guards some Italian POW then suspicion falls on Walker that he may be helping them to escape. Mainwaring then sets a trap with a surprising outcome.

Capt. Mainwaring has the idea of small armed patrols to wreak havoc upon the enemy using a small re-processed boat the bank has acquired. After a practice on the river they get lost in the fog, and thinking they have drifted across the channel and are about to be captured by the Germans, they are in for a shock when they find out where they really are.

In Capt. Mainwaring's absence Wilson organises a darts match against the ARP in the local pub. When Mainwaring returns unexpectedly they have trouble getting the men back on parade.

After listening to a radio broadcast asking for men to form what was to become known as the Home Guard, George Mainwaring, a local bank manager, decides to act and form the platoon of his own accord. He appoints himself as Captain and recruits his chief bank clerk Arthur Wilson as the platoon sergeant as well as enlisting the bank's office boy Frank Pike. Several of the local tradesmen - including James Frazer, a philatelist shopkeeper; retired shop worker Charles Godfrey; Jack Jones the butcher and black market businessman Joe Walker - also volunteer their service for 'King and Country.' And so, The Walmington-on-Sea Home Guard was born.

With the shortage of weapons, Capt. Mainwaring goes to the local museum to see if any of the guns on display can be used by the platoon.

Capt. Mainwaring, worried about the lack of weapons, gets a visit from Col. Square, an old soldier who offers to donate some guns from his collection, providing he can take command of the platoon. Mainwaring agrees until he sees the state of the guns.

Capt. Mainwaring is giving a lecture on recognising enemy agents when he learns that for every Nazi captured there is a reward. Later on Jones and Walker capture two Luftwaffe airmen, although a Polish officer intends to claim the reward. Back at HQ the airmen escape on Godfrey's watch.

Just when the platoon finally gets its uniforms, LCpl. Jones is told that unless he can complete the assault course in 15 minutes he will have to leave, so Mainwaring and the rest of the platoon think of a plan to help him.

When news that the Prime Minister is to pay a visit to the area a shooting contest is held to see which of the local platoons will form the honour guard. Walker gets a crack shot from the theatre touring show (Barbara Windsor) to take part as a member of the platoon but a surprise is in store for everybody.

When six members of the Highland Regiment attack the Warmington-on-Sea's HQ, the platoon has to come up with a scheme to capture the attackers.

When the church bells start to ring, the platoon leaps into action. Jones takes half the platoon to Godfrey's cottage to set up a machine gun post while Wilson, not knowing where Jones has gone, also heads for the cottage where they both mistake each other for the enemy and prepare to attack.

Walker is finally called up but Mainwaring tries to get his call-up deferred because of his value to the platoon, but he is still conscripted, only to find out that he is allergic to the army's corned beef.

Sgt. Wilson overhears Mrs. Pike telling Frank that she is expecting a child. Wilson assumes that she is pregnant and that he is the father, but it turns out that she is looking after an evacuee. Mainwaring advises that Wilson marry her, until she clears up the misunderstanding.

Capt. Mainwaring promotes Frazer to Lance Corporal, thus causing friction between him and Jones. When Frazer starts getting above himself, Mainwaring cancels the promotion.

The platoon is fire watching when the men see a man using a torch. Convinced that they have discovered a spy, they arrest him only to find that they have made a terrible mistake.

Mainwaring is under orders to be more co-operative with the ARP wardens; a task that's made very difficult by their newly appointed chief. Walker strikes a deal with Jones to make it easier for him to carry rationed goods without being stopped by the police - he is to let the platoon use his butcher's van as a troop carrier and ambulance by day and let Walker use it by night. He bribes Jones with the promise that Jones will receive petrol coupons for it. Unfortunately things don't entirely go to plan...

The platoon travels to a secret location to be trained at a battle school. After a long train journey and a march in which they get hopelessly lost, they arrive late and end up missing two meals and the third is virtually inedible. Starving and tired the platoon tackles the assault course in which they try their best to get back at Mainwaring for getting them lost. The platoon then has to capture the 'enemy's camp' held by Capt. Rodrigues and his men. This task looks impossible but can Mainwaring save the day and win back the respect of his troops? Meanwhile Walker tries to raid the nearby farm to get food for his starving comrades.

Capt. Mainwaring teaches the platoon the tactical use of the phone system when a German plane crashes into the town's reservoir. Because Mainwaring and Wilson cannot decide what to do it is left to Walker to come up with a plan to make the Germans surrender.

When a low-flying German aircraft attacks Warmington-on-Sea, the platoon, under the command of LCpl Jones, fires at the aircraft and uses up all its ammunition. Mainwaring is furious and orders an investigation.

The bank takes a direct hit during an air-raid, but the bomb fails to explode, leaving Mainwaring and Wilson stuck in the vault with it. When the bomb disposal officer leaves to collect the right tools, the platoon members take matters into their own hands.

Capt. Mainwaring is found not to have held the King's Commission so he is reduced to the ranks and Sgt. Wilson takes over command of the platoon. After a disastrous war game against the Eastgate Platoon, his men ask the Colonel for him to be reinstated.

The platoon is given a heavy naval artillery piece but the town's bandstand, a rare example of Victorian ironwork, stands in its field of fire. The town council insists it must be preserved but Mainwaring reasons that a demonstration of the gun's capabilities will quiet any protests.

The platoon captures a runaway barrage balloon and while trying to secure it, Capt. Mainwaring is carried aloft.

The platoon holds a dance where Pike is going to announce his engagement to a local girl. Sgt. Wilson tries to get him to change his mind but Pike will not be put off.

The platoon is assigned guard duty on an isolated, disused pier for a week. However, thanks to Pike's poor judgement over how to moor the boat, they end up stranded with no contact with the mainland and no food. Attempts at Morse code only prompt Hodges to pursue the platoon to get them to 'Put that light out!' and he ends up stranded himself. If that wasn't enough, Jones spots a stray mine under the pier, but does Hodges have a solution that'll 'bowl them over'?