Episode 2

The bombers are out there again, and this time they are good. The investigation is chasing perpetrators whose skill and sophistication keep them one step ahead, and the episode builds its pace around the simple, grinding difficulty of catching people who clearly know what they are doing. It is the sort of enemy that makes a procedural earn its keep. They are never where the police expect, and never quite where the last lead said they would be.

The manhunt presses on through one stalled line of enquiry after another, and the pressure mounts on everyone involved. Progress is hard won. Then a breakthrough finally arrives, and it comes from Helen, who pushes through the surrounding frustration to reach a conclusion that moves the case forward properly. It is a reminder that in this line of work, advances are usually made by somebody refusing to let go of a detail. Every dead end still teaches them something, even when it feels like wasted time. Helen's breakthrough is the sort of quiet victory the show does well. The clock is never far from the frame.

Simon Ashdown and Daniel Brierley wrote it, Jon East directed it, and the cast is deep. Vicky McClure shines as Lana, with Thom Ashley's Nick Hood and Rose Basista's Suzie beside her. Lee Colley's Hanson, Bethan Cullinane's Hope and Tomiwa Edun's Alex fill out the working team, Alexander Eliot's Luke and Kevin Eldon's Jeff Washington add to the picture, and Nabil Elouahabi's Hassan Rahim and Kerry Godliman's Sonya Reeves keep the links to the earlier series in place. Nobody in the ensemble is wasted.

It is satisfying when a crime drama trusts the methodical process of deduction to carry the tension. This one does. The hunt is the story, and that is exactly right. Patience is a virtue in this genre, and here it pays.