In 2003, John Porter leads a team of Special Forces soldiers, including military intelligence officer Hugh Collinson, on a hostage extraction in Basra, Iraq. Porter is confronted with an Iraqi child suicide bomber on the stairs of a terrorist safe house. When he allows his emotions to get the better of him, the operation goes disastrously awry. Only Porter and Collinson survive, two men are killed and one is left gravely injured. Racked with guilt, Porter quits the army and his life falls apart.
Seven years later, British TV news reporter Katie Dartmouth is kidnapped just outside Basra. News of the kidnap reaches Collinson, now the head of military intelligence at Section 20. On seeing a photograph of one of the suspects, both Collinson and Porter, who is now working as a security guard at Section 20, recognize the bomber they encountered in Basra.
Convinced that Darthmouth's kidnapping is connected to the events they witnessed in 2003, Porter begs Collinson to let him go back to Basra to search for the terrorist cell, The Sword of Islam. Collinson agrees to reactivate Porter for duty.
Porter accompanies Section 20 operative Layla Thompson and a Special Forces team to Basra. As Layla and the Alpha Team head to the identified location to rescue Katie, Porter is left behind. The mission goes drastically wrong and only Layla returns to base. Alone, Porter sets out to retrace his steps and relocate the scene of the 2003 operation.