Lana, an explosives disposal officer with the London Metropolitan Police, and her senior officer Nat are called to West Haven public housing to handle an explosive device. Inside the apartment, a man's wife and child are found bound. The bomb discovered in the bathroom is identified as fireworks powder, incapable of causing injury.

After the West Haven explosion, Lana is called to a briefing with the Counter-Terrorism Command and the Security Bureau, where Hamilton asks her to become the bomb squad leader. After Nat's funeral, Lana gets drunk at a bar. Meanwhile, a van captured on surveillance camera is found at the building where the bomb was planted.

Lana attempts to stop the mosque bombing but fails, and the far-right group “Crusaders” claims responsibility. Furious that John didn't help defuse the bomb, Lana receives a report that a bomb has been planted in an LGBT pub. While investigating, she is shot by an unknown assailant.

Following the LGBT bar bombing, suspicions grow that a series of explosions are the work of the “Crusaders.” Lana suspects John's involvement and becomes convinced the perpetrator is someone with military training. Meanwhile, Lana's brother Billy is arrested for attacking a Muslim-owned store, revealing a connection to the “Crusaders.”

Heartbroken over losing Billy, Lana rejects Thom's offer to move in together. The Counter-Terrorism Headquarters uncovers the involvement of Frank Welsh, a former soldier and far-right extremist, and launches an investigation. Lana returns to duty on the condition of counseling. Meanwhile, Sonya obtains the files on the explosive HMX319.

[Season Finale]The Counter-Terrorism Command was searching for John when he sent Lana the number for Steepholm, an undisclosed military weapons depot storing HMX319. A soldier had died in an accident during HMX transport there, and the bereaved family suspected foul play, demanding the investigation files be released.