Ghost

Rachel comes back to Syndicate 9 after a year away on vice, steps into the acting DI role, and is immediately given a murder that turns out to be bigger than it looked. Michael Edgerton's death is shocking enough on its own. Then a teenage boy finds a clip of the killing on the darknet, and it becomes clear that this was not a single, indiscriminate murder. It is a game, and the team has to find the next potential victim before the person playing it does. The darknet clip means the murder has an audience, and that changes the maths of the investigation completely.

There is a lot of catching up to do with Janet, whose friendship Rachel neglected while she was away. Janet is glad to have her back, and it turns out she needs her sooner than anyone expected. Taisie is arrested, setting off a chain of events nobody saw coming, and Janet is thrown into turmoil. Rachel's experience and quiet wisdom are exactly what steers her through it. It is the friendship working the way it used to, before everything got complicated.

The episode runs on a new rhythm: Dodson watches from above, and Rachel is under pressure to perform in a role she has not worn before. The case is the kind this show does well, because the threat is not just a killer on the loose but an audience for the killing. There is no comfort in any of it, and the episode does not pretend otherwise.

Lee Warburton, Diane Taylor and Sally Wainwright wrote it, Alex Kalymnios directed. Suranne Jones leads as Rachel, with Lesley Sharp's Janet, Jing Lusi's Anna Ram, Pippa Haywood's Dodson, Judy Holt's Scary Mary and Louis Healy's Maurice Ridley in support.

A murder recorded and shared is a different beast from a murder investigated, and the show knows it. Rachel is back, and the ground has moved under her feet while she was gone.