The Colonel orders the platoon to make a training film with a couple of well-known actors, but unknown to Mainwaring, they're to play the Germans. Although Mainwaring refuses to participate, the rest of the platoon is still ordered to do so. When filming is cancelled, Mainwaring and the men, still dressed as German soldiers, are spotted in the local pub and the alarm is raised.

Pike finally gets his call-up papers for the RAF, but when his blood donation to the Red Cross is checked, it is found to be from a rare group and he is designated exempt. But now he has to find a way to break the news to the platoon.

At the bank, Mainwaring's office door is replaced with one made of paper. Adding insult to injury of not having a proper entryway, Mainwaring is more annoyed at Pike, the Colonel, and Jones destroying it within minutes of installation. Meanwhile, Godfrey's cottage is due for demolishment to make way for a new airfield but no one can bring themselves to break the news until Jones finds out that he already knows.

Mainwaring gives a lecture on field craft in the vicar's garden, covering what to eat and how to erect a tent. Later, apart from having to put up with the vicar, verger, Hodges, and a gang of boy scouts, their field manoeuvres are interrupted by three downed German airmen trapped in their dinghy in the middle of the lake. 'Hӓnde hoch! Hӓnde hoch!'

When Mainwaring tries to help Jones with his fiduciary issues, the trail is discovered to lead through the platoon, on to Mavis Pike, and ends with Hodges.

Mainwaring has visions of promotion for himself and Wilson, and of expanding the platoon into a company, so he embarks on a recruitment drive. A poster is drawn up and Jones is voted to be on it. Unfortunately, a mix-up at the printer's results in Jones being branded an escaped POW instead.