Trade

Season four opens with the case nobody would volunteer for. Street prostitutes are being murdered, one after another, and Chappel is the one holding the file. The investigation is barely underway before he breaks his own rule and gets involved with one of the women, a young prostitute called Sandra, and from that moment his judgement has a hole in it.

Her new friend makes it worse. Gordon Ellis is a City futures trader, sleek and sure of himself, the sort of man who treats a kind word as a transaction. Chappel is convinced Ellis is behind the murders, and he may be right. But he is also competing with the man for Sandra's attention, which means every conclusion he reaches has to be checked twice, mostly by the audience. That is the point, and the episode is honest about it.

The show handles the tension well. Chappel's certainty is real and his motives are muddled, and the episode keeps both true at once. James Frain plays Ellis with the polished menace of someone who has never once been told no, and Emma Catherwood's Sandra is nobody's pawn, which is what makes the triangle matter.

Around them the squad strains. Superintendent Archer keeps the pressure on from above, and Hutchins and Morgan do the kind of steady work that never makes the headlines. John Lloyd Fillingham's Darren McIntyre and Emma Buckley's Angie fill out the world of the dead women and the ones still working, and John Macaulay is a security officer who turns up at the wrong moment.

Clive Bradley wrote it, Justin Chadwick directed. It is a strong, sour start to the year, and its best decision is refusing to make anyone easy to root for. Sandra keeps her agency, Ellis keeps his charm, and what Chappel keeps is the mess. There is no comfort in the ending, which is probably the correct call for a show that opens a series this way.