Big Boys' Rules (1) (master); Wikipedia "Big Boys' Rules (Part One)"; IMDb "Big Boys' Rules: Part I"

Declan Harris is found murdered in Epping Forest, and the body carries a question with it: Harris was a Special Branch informer, forced into it, and the suspicion is that the Branch itself killed him. Clark takes the case, and it's the chance he's been waiting for to settle old scores with Deakin.

J. C. Wilsher wrote it, Richard Standeven directed, and the episode is a half of a story that knows it's a half. Naylor, newly transferred, works a separate murder case with a boss who wants it closed yesterday, and his principal suspect is Simon Bridge, the victim's nephew. Harris had recently contacted Insp. Dilke, played by David Morrissey, and Dilke had him down as a fantasist, which is a detail that will not age well. The press has a field day with Harris's death, and the headlines become part of the pressure the enquiry works under.

But the other thread is Deakin, seen in conversation with Trevor Bull, an armed robber described as extremely violent. Frank Harper plays Bull with the kind of coiled stillness that makes you believe the description. Robin Ellis, the original Ross Poldark, is Donald Berridge, one more face from an earlier era of British television. Whatever Deakin and Bull are cooking, Clark can smell it, and the pressure is on him to produce a quick, convenient result that lets everyone breathe out.

It's a setup episode in the best sense: every piece placed, every tension wound, and the two investigations pulling toward each other like magnets. The informant's death, the nephew's guilt or innocence, Deakin's scheming, Bull's violence. None of it resolves, because the second half is where the bills come due. The Epping Forest setting gives the murder a cold, open-air loneliness, a body found among trees that have seen worse. And the episode's willingness to split its time between Clark and Naylor's separate cases pays off, because the two investigations are clearly heading for the same collision.