Episode 4

After the violent attack she suffered in prison, Lindsay Denton is granted special dispensation to visit her dying mother. It is a small mercy in a season that has not been generous with them, and the episode lets the visit breathe. Meanwhile, Deputy Chief Constable Mike Dryden keeps shrugging off the allegations about his relationship with Lindsay and any possible link to the ambush. Two people under suspicion, each pretending the storm will pass. The visit is watched, logged and timed, because that is what this world does to kindness.

The episode is at its best in the quiet scenes: a hospital bed, a daughter trying to say goodbye while the force watches her. The professional and the personal have never been cleanly separated in this show, and here they bleed into each other. Dryden's denials grow thinner as the suspicion around him thickens, and the question of what he knew about the ambush refuses to go away. The investigation keeps moving in the background, and the two storylines pull against each other the way they should. It is the rare episode of this show where the saddest scene is not an interview.

Jed Mercurio wrote it, Daniel Nettheim directed. Keeley Hawes gives Denton a weary dignity that keeps the sympathy alive, and Mark Bonnar makes Dryden slippery without making him cartoonish. Martin Compston's Arnott, Vicky McClure's Fleming, Christina Chong's Rogerson, Adrian Dunbar's Hastings, Andrea Irvine's Roisin, Craig Parkinson's Cottan, Simon Coury's Lightwater and Lucy Cray-Miller's Regan complete the cast. The ensemble is dependable, and the episode knows how to use it.

It says something for the writing that the procedural elements never smother the human ones. The episode remembers that the people at the centre of these cases have mothers, and families, and lives outside the incident room. And it is a better episode for remembering. It is a quiet hour, and the show is not ashamed of that. The goodbye is the thing you carry out of it.