The EXPO team are stretched to breaking point dealing with a complicated device planted at the Campaign HQ of the Progressive Alliance. Lana tells Karl she wants to break up.

Lana begins to explore her grief with the help of a clinical psychologist and begs Hamilton to allow her to resume her professional duties. The explosives team is called out to a device targeting a radio station covering the upcoming by-election, leading counter-terrorism officers to suspect a connection between the Progressive Alliance and the bombing campaign.

Sonya manages to trace the chemical explosive HMX used by the bombers to a government lab at Porton Down, but runs up against a wall of silence when she pushes for more information. Lana demonstrates to Thom that the wiring within the devices shows evidence of advanced bomb-making skills, leading her to suspect members of her own team.

A far-right group called the Crusaders claims responsibility for the mosque attack, declaring it is in revenge for the Westhaven bombing, while counter-terrorism officers scramble to identify the bomber from CCTV footage. Working with the bomb data centre, Lana finds a forensic link between the explosives used at both sites - suggesting it might be the same bomber.

CCTV footage of a suspicious vehicle leaving Westhaven leads Washington and the team to a warehouse on the edge of London, where they uncover bomb-making materials and evidence that seems to confirm that the bombers were Islamist. But the discovery of what appears to be military equipment and high-grade explosives on site makes Lana question the real identities of the bombers, and a further device left in a sensitive and provocative location seems to confirm her suspicions.

Bomb disposal officers Lana Washington and Joel Nutkins are called out to a Met counter-terrorism operation at a London housing estate to investigate a potential bomb factory and suspected bomb-maker Andy Phelan.