Episode 1

DCI Roz Huntley has spent months chasing a serial killer, and the pressure from her superiors is enormous. When another young woman is abducted, Roz is on the scene, and she tracks down a 24-year-old man and charges him. The doubts start almost immediately. The chief forensic investigator, Tim Ifield, flags the case to AC-12, and the suggestion is that a miscarriage of justice may be in progress.

The episode is built around the question of what Roz is ignoring. Is she overlooking forensic evidence that might prove the young man's innocence, and is she doing it on purpose? Hastings sends Kate Fleming undercover inside Roz's team to dig deeper, while Arnott piles on pressure from the outside. Roz, a mother of two with a husband named Nick, is the sort of woman who will do anything to stop her life unravelling, and the show lets that hang over everything she does. Every scene with the team is a small study in how a confident investigation starts to wobble.

Jed Mercurio wrote it and directed it. Thandiwe Newton is formidable as Roz, all efficiency and buried fear, and Jason Watkins makes Ifield's quiet decency the trigger for the whole story. Vicky McClure's Fleming, Martin Compston's Arnott, Adrian Dunbar's Hastings, Gaite Jansen's Reznikova, Claudia Jessie's Taylor, Kwame Che Kandekore's Ollie, Mark Stobbart's Twyler, Seamus O'Hara's arresting officer, Scott Reid's Farmer and Henry Miller's Morganstaff complete the cast.

The episode is about the danger a system poses to the people it is meant to protect, and it earns that theme the hard way. Roz is not a villain in the usual sense. But she is a woman under pressure making choices, and the show is interested in what those choices cost. The man at the centre of the case is barely a presence, which is its own kind of statement. It is a strong opening, and it does not pretend the answers will be clean.