Explosives Officers Lana Washington and Joel Nutkins are called out to investigate a potential bomb factory in a London housing estate, but there's no sign of the bomb makers. Washington and Nutkins defuse an IED, but its complexity suggests they're dealing with sophisticated terrorists. As the police evacuate residents from the estate, an even deadlier terrorist threat emerges and Lana and Joel work against the clock to save as many lives as possible.

As the bombing campaign intensifies, Explosives Officer Lana Washington attempts to solve the mystery of who is behind the terrifying attacks. Inter-community tensions rise as the far-right group English Flag and their leader Agatha Jack take to the streets to blame Islamists for the attack. CCTV footage of a suspicious vehicle leaving Westhaven leads the team to a warehouse on the edge of London.

A far-right group called the Crusaders claim responsibility for the mosque attack. Lana finds a forensic link between the bomb at the mosque and the one at Westhaven and they might have been bombed by the same person.

Following the murder of a Counter Terrorism officer, Lana Washington and the EXPO team race against time to stop the bombers before they strike again. 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 further 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 EXPO team.

Lana struggles to come to terms with her personal loss, and her failure to prevent the explosion. Meanwhile, Counter Terrorism officers identify the bomber and launch a massive manhunt, and the EXPO team are called out to a device targeting a radio station who are covering the upcoming by-election.

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. As polling day arrives, security is ramped up at the returning station, where both Ayesha Campbell Khan and Agatha Jack are expected.