Joker

Every force has a bad apple, and 'Joker' is about what happens when the bad apple is one of your own. A fellow detective tries to pin a jewellery theft on an old villain, and Maggie has to work out whether it is a stitch-up, a mistake, or something worse. That is the neat trick of the episode: it makes you uncomfortable about your own instincts. The awkward part is that the framed man is the sort of character the squad would normally be happy to see go down.

Ray Jenkins and Terence Feely wrote it, Nic Phillips directed, and it went out on 10 December 1982. The title is a card-playing joke and also a description of the man doing the framing; Enn Reitel's TDC Power is smooth enough to make you almost root for him, which is exactly the trap. Susan Edmonstone's Margaret Sloan, Don McKillop's Eric, David Oakley's Harry and Alan Lake's Malcolm Webster circle the case, each carrying a piece of the story. Who the villain is matters less than whether the evidence against him survives a proper look.

The pleasure of the episode is watching Maggie pull on the thread without knowing where it leads. She has to accuse a colleague of corruption, which is a career-ending move if she is wrong, and the script keeps that weight visible. Russell, Croft, Barratt and Phillips do their usual supporting work, but this one belongs to her. There is no explosion and no chase; just paperwork, interviews and the slow peeling of a lie.

It is a proper departmental affair, the kind of story the series did better than most. But corruption inside the job is a nastier enemy than any villain, and the episode knows it. Maggie ends the episode with one colleague grateful and another ruined, and you are not sure which feeling should win. The last laugh belongs to the title, and it is not a kind one.