Powerline

An undercover agent named Shirley is killed in a lonely patch of woodland, and Fred and Tessa go after her killers posing as travellers. They join a band of nomadic religious people camping rough on Lord Leydon's estate, which means the episode gets to do that thing eighties television loved: two city women in a field, trying to look like they belong there.

Tessa, meanwhile, visits James Leydon at the Manor House and finds a man who already suspects her of working with the thought police. The threads tie together through Barbara Dalchley, a friend of Jamie's who is in league with Sergei, a Russian defector, and Seth, one of the travellers whose real job is photographing nuclear missile bases. When the camper van is sabotaged, a security patrol has to pull Fred and Tessa out, and the episode ends with Tessa in a shoot-out. The Leydon estate is the sort of place where everyone knows everyone and trusts no one, which suits the unit's business perfectly.

Terence Feely wrote it and Ian Sharp directed. Leslie Ash's Fred and Tracy-Louise Ward's Tessa share the load, with Dorothy Ford as Shirley, Trevor Byfield as Harris, Peter Jonfield as Lawson, Lesley Nightingale as Lucy and Isabella Marsh as Lucy's Baby, while Jill Gascoine's Maggie and Don Warrington's Nigel keep the home end going.

There is a faintly silly strand to the travellers, all beards and blankets, but the show plays them straight enough that the spy business underneath stays properly tense. And the estate, big and empty and watched, makes a good setting for paranoia. Nobody in it is quite who they say they are, which is the whole point. The shoot-out ending is abrupt, the way good endings often are, and it leaves the case feeling less tidy than the show usually allows.