Stranger in the House

Denton is terrorised by a rapist with a signature method: he slips into the homes of his victims, people whose jobs involve wearing uniforms, and he waits. The attacks leave families traumatised — one victim attempts suicide — and the station, already stretched, is flailing. Frost is assigned WPC Hazel Wallace as support, the first significant storyline for the character Caroline Harker would play for years.

Seventeen-year-old Alison Cook goes missing, presumed taken by the rapist, but she comes back of her own accord: she had bolted after discovering her mother's affair. The detour matters, because her father Martin draws suspicion; he had done odd jobs for some of the victims — until it emerges that Martin is impotent and fully aware of his wife's betrayal, a suspect destroyed by humiliation rather than guilt.

Frost pieces the pattern together the way he always does, with stubborn observation: each victim lived near open ground, which narrows the search area dramatically. He sets a trap with Wallace, and the masked attacker is tracked to Gordon Perryman, a night-shift security guard with a burgling habit. But Perryman is a cover. His partner, Nick Daish, is the rapist — a man who hides inside other people's lives as casually as he hides in their homes. Daish confronts Wallace at her own flat, and she manages to incapacitate him just before Frost arrives. In the cell, Daish admits it with a grin: he enjoyed taking power from women. Len Collin makes the confession genuinely chilling, all the more so for its flatness.

Beneath the horror, the episode quietly advances Frost's personal life. He invites Shirley Fisher to a Victoria Cross and George Cross holders' reunion in London, but the case swallows him and he arrives too late to meet her. Stranger in the House, written by Christopher Russell and directed by Don Leaver, is the season finale, and it closes on a note of promise and regret: a villain caught, a romance nearly kept, and a detective who can never quite be in two places at once.

The finale of the second season leaves Frost at a familiar crossroads — the case won, the personal life missed by inches. It is a pattern the series would repeat for another sixteen years, and it never once stops working. A strong finish to the season, capped by a chilling confession.