Alibi

Alibi is about the flimsiest word in policing. A string of robberies has the town on edge, and PC Danny Sparks finds himself in the position of providing someone with a defence against the accusations. The question the episode keeps turning over is how far an alibi holds when it rests on memory and goodwill, and on the gaps in between. An alibi is only as good as the person giving it, and everyone in the station knows it. Sparks vouches for someone, and the vouching is the story.

Inspector Kate Longton, Sergeant Joseph Beck and Sergeant George Parrish work the case around Sparks's contribution, with Detective Inspector Peter Bradshaw, played by Martin Cochrane, on the detective side. The community supplies the witnesses: Pip Miller's Mike Laine, Julia Lewis's Jenny, Emma Piper's Marge and Charu Bala Chokshi's shopkeeper. Each witness remembers a different version of the same hours, and the discrepancies start to matter. The shopkeeper's testimony is the sort of small detail the show loves. For a quiet episode, it keeps a surprising amount of suspense going.

Wally K. Daly wrote it, Graeme Harper directed. Anna Carteret is Kate Longton, with David Ellison as Beck, Noel Collins as Parrish, Mark Botham as Sparks and C.J. Allen as Kelleher. Pip Miller plays Mike Laine, Martin Cochrane is Peter Bradshaw, Julia Lewis is Jenny, Emma Piper is Marge and Charu Bala Chokshi is the shopkeeper.

What makes the episode tick is how easily a solid-sounding story unravels. And everybody's timeline has holes in it. The case becomes a contest over who can make their holes look like the other person's. Nobody is lying outright, which is the point; honest people misremember, and the law has to do something with that. Longton lets the case breathe, and the breathing is where the cracks show. It is a concentrated hour on circumstantial evidence, and a reminder that in Hartley the truth usually has a timetable. The resolution, when it comes, feels earned.