Trial & Retribution VI (2)

The second night of this case opens with the sort of detail that stays with you: a single tooth, belonging to the abducted woman, recovered from the debris of a wood chipper. It is a grim piece of evidence and the programme treats it as exactly that, a cold forensic fact around which everything else has to be built. Whatever happened to her, the machine has done the work of making it hard to prove.

Alongside the forensics runs a smaller, uglier story. Walker's ex-wife has a new boyfriend, and over these two nights he slides into outright psychosis. The show cuts between the methodical police work and this private unravelling without ever quite forcing a connection on you; both threads simply head towards their own reckoning, and you watch them go.

Pat North carries the investigation, Kate Buffery playing her with the weary competence the role needs, and Inday Ba is D.C. Lisa West at her side. Juliette Cheveley returns as Jane Mellor, one of the girls who saw the abduction. The supporting roster leans towards the machinery of justice rather than the street: Gregory Cox as a selection panel chairman, Richard Durden as Dr. John Foster, Bella Emberg as Mrs. Fowler, David Fairweather as Mr. Tulley and Cate Fowler as a clerk, plus James Ford as Donny Brickman and Camille Coduri as Sharon Fearnley.

No writer or director is credited for this instalment, which is unusual for the series and worth noting rather than papering over.

It ends up being an episode about two kinds of evidence. One kind comes out of a wood chipper and can be bagged and tagged. The other kind walks into a room talking to people who aren't there, and no procedure in the world covers that. The show gives both the same flat, unblinking attention, which is its oldest trick and still its best one.