Episode 4

Catherine's depression has sharpened into something like purpose. Kirsten's death is still with her, and it sends her back onto the hunt for Tommy Lee Royce with a new edge, the kind that makes colleagues step out of her way. Ashley Cowgill can feel the net closing, so he gives Tommy an order: get rid of Ann Gallagher. Tommy doesn't get rid of her. He takes her prisoner in his mother's cellar, which keeps her alive and makes everything worse at the same time.

Catherine follows a hunch and gets a face-to-face meeting with Helen, Nevison's wife. Helen admits everything, and the truth lands with the weight Catherine has been carrying for years. It should be a breakthrough. Instead Royce finds her and assaults her, murderously, and both women end up fighting for their lives. The episode's last act is as close as this show gets to horror: a cellar, a locked door, and a man with nothing left to lose.

The two women end up in the same fight even though they started on opposite sides of it. Ann was the daughter taken as a bargaining chip, the reason the whole mess began; Catherine is the copper who never let the case go. In the dark of that cellar the distinctions stop mattering. They are just two people trying to live through a man who has decided otherwise, and the cellar is Tommy's mother's, which matters too: even his cruelty is a family affair, kept close and handed down.

Sally Wainwright wrote and directed this one herself. Sarah Lancashire plays Catherine's worn-down fury with her usual control, and she is backed by James Norton's Tommy, Joe Armstrong's Ashley, Charlie Murphy's Ann, Steve Pemberton's Kevin, George Costigan's Nevison, Shane Zaza's Shafiq, Rick Warden's Mike Taylor, Adam Long's Lewis and Rachel Leskovac's Julie Mulligan.

The episode is a reminder that this show's heroes don't get clean wins. Catherine gets the truth she wanted. The cost is nearly everything.