Wilt is back - in form, and in a good deal of trouble.
Henry Wilt is still teaching at the Fenland Tech, attempting to drill English into plasterers, dozing through tedious committee meetings and occasionally getting mildly plastered in 'The Pig in a Poke' with one of his few bearable colleagues. But the even tenor of his days is rudely interrupted when the shadow of drug dealing flickers across the Tech. Suddenly Wilt becomes the target of suspicion. His colleagues believe him to be responsible for triggering a departmental inquiry, and his old adversary Inspector Flint, knowing that he's guilty of something, sees a chance to settle a number of scores.
What starts with an accusation of voyeurism in the staff lavatory (of the wrong gender to boot) leads, more or less directly, to a massive confrontation at a nearby US airbase with the forces of law and order on both sides and Wilt in his usual place - in the middle.