Episode 4

A Counter Terrorism officer has been murdered, and the EXPO team are suddenly racing the clock. Lana Washington and her colleagues have to assume the bombers will strike again, and the whole hour is built around the gap between those two facts: a killing they were too late to stop, and a plot they cannot yet see. This is the episode where the threat stops being a theory and starts being personal. The murder of one of their own does that. Every minute they lose edges them closer to the next bang.

But the pace is taut from the first scene. Washington and the team scramble to piece together what happened, then to anticipate what comes next, and the danger feels immediate in every room they search and every door they approach. Nobody here has time to be decorative. The momentum is relentless, driven by the sense of an impending strike that none of them can pin down. Waiting, the episode understands, is its own kind of horror.

Daniel Brierley wrote it and Jennie Darnell directed it, a new pair of hands behind the camera this time. The ensemble holds up its end. Cal MacAninch's Inspector Lee Robins and Kris Hitchen's John Hudson are there again, with Ralph Ineson's Commander Bregman adding weight to the command structure and Nadine Marshall's DSU Marianne Hamilton in the mix. Ewan Mitchell's Billy Washington is never far away. Supporting the investigation are Gwynfor Jones as PS Brown, Tom Stokes as Pete, Gavin Sibson as PS Costa, Lucy Russell as Moira Bloxham and Nabil Elouahabi as Hassan Rahim.

It is a welcome reminder of what a tightly plotted procedural can do when the performances underneath it are this committed. There is no fat on it. The hour moves, and it makes you move with it. One of the stronger episodes of the series so far, for my money.