Benefit of the Doubt (1)

Frost is being impersonated. A man is going around Denton pretending to be the famous detective, using the name to gain trust and sexually assault women — a grotesque parody of everything Frost stands for, and a thread that runs through the whole two-parter. Worse, a young woman named Anne has turned up claiming Frost is her father, and the timing could not be worse: he has been assigned a new officer, DS Terry Reid, abruptly transferred after the influential father of a student lodged a complaint student Reid suspected of selling contraband cigarettes.

The case that opens the episode is brutal. A woman, Sylvia Carter, is found dismembered on the railway tracks, struck by successive trains; she worked for a local sandwich maker, and Frost is sure she was having an affair and quietly selling surplus stock — a small life with a terrible end. Meanwhile, Dr Helena Gibson, a senior surgeon disliked by nearly everyone at the hospital, goes missing over a weekend. She had been fighting her cost-cutting boss Jameson for proper funding for her department, and her abrasive personality leaves no shortage of suspects.

Frost and Reid work the two cases in tandem, the mismatch of styles — Reid careful and wounded, Frost instinctive and impatient — slowly hardening into respect. The episode's best running joke is the Frost impostor, who keeps turning up in Reid's own investigations, blurring the line between the detective and his double.

Benefit of the Doubt (1), written by David Gilman and directed by Roger Bamford, opens the eighth season with Frost under assault on every front: his reputation stolen by an impostor, his paternity questioned by a stranger, and his new partner carrying a grudge from a system that loves to punish the honest. Joanne Froggatt, years before Downton Abbey, brings Anne a poignant gravity, and Robert Glenister's Reid is the most complicated partner Frost has ever had.

An episode about identity — the impostor wearing Frost's name, the daughter who may not be his, the partner nursing old wounds — and a season opener with rare emotional range. A season opener about identity, in every sense.