Episode 5

David Budd's theory is hardening into something he cannot shake: the people who killed Julia Montague are inside the machine. This episode lets him chase that idea, and lets everyone else start wondering whether he is chasing shadows.

Rayburn finds the pre-attack CCTV has been tampered with. Budd builds an E-FIT of Longcross. SO15 puts a name to Apsted, and his old job as an army EOD officer makes him a plausible bomb-maker. Budd reads up on the kompromat Montague was given and ambushes Roger Penhaligon at his constituency surgery, accusing him of trying to lift the tablet while she lay in hospital. But a meeting with a gun dealer goes badly: Budd wants the same model of sniper rifle Apsted used, and it attracts the attention of Luke Aikens, a powerful crime lord with a seat at the conspiracy's table. Chanel Dyson, the PR Montague fired, buys Budd a coffee and invites him for drinks. He gives her his number. The Range Rover that collects her is the one that picked her up the day she was sacked, and Aikens is driving.

The leak of Budd's relationship with Montague reaches the press, and he starts to suspect her hotel room was bugged. It is the least of his problems. His colleague Tom Fenton raises the head injury Budd gave himself, and Lorraine Craddock suspends him from duty and revokes his firearms licence. Later, in Montague's flat, Budd finds the tablet hidden in a photo frame.

Jed Mercurio and John Strickland share the credits again. The supporting cast is doing sharp work: Gina McKee's Sampson, Ash Tandon's Sharma, Pippa Haywood's Craddock, Stephanie Hyam's Dyson, Matt Stokoe's Aikens, Michael Ryan's gun dealer and Michael Shaeffer's Longcross.

There is a point in every conspiracy thriller where the lone believer looks like the problem rather than the solution. The show plays that beat well, and the suspension lands harder than any of the action so far.