Vulnerable

Eunice Bevan's body is found in her own house, and her bed-ridden husband Joe lies in the room above. There is no sign of forced entry, so the killer must be one of the Bevans' children. The house itself is the witness here, and it has been keeping secrets for decades. The only one still around is Helen, who says she has not spoken to her parents in thirty years. Joe is convinced he heard Helen arguing with her mother, and Helen is arrested.

Helen tells Rachel the rest of the story: the parents abused her and her siblings, and one of them later took their own life. It puts a very different light on the old man upstairs. Janet, now acting sergeant, notices that Joe is far more mobile than he claims to be. The mobility detail is the one that cracks the story open. The police reasoning narrows to an ugly choice: one of the two surviving occupants of that house is responsible.

Rachel is having doubts about marrying Sean, and her loud, drunken mother Sharon reappears, which does not help. Janet, when a concerned neighbour knocks on her door, begins to realise her own marriage is finished. The knock on the door is the kind of small event that rearranges a whole life, and the episode treats it with respect. Neither woman gets to deal with one crisis at a time; the show has never worked that way.

Sally Wainwright, Diane Taylor and Suranne Jones wrote it, Morag Fullarton directed. Suranne Jones's Rachel, Lesley Sharp's Janet and Amelia Bullmore's Gill lead, with Rayna Campbell as Ginny, Marc Parry as DI Brian, and the familiar squad in support.

A locked-house mystery where the real horror is the history, not the door. The title says it all, for once. And neither of our two detectives is in any position to enjoy the win, assuming there is one. It is a strong start to the series, and an uncomfortable one.