After acting on poor intelligence, officer Paul Tallis shoots a suspected terrorist in a Birmingham shopping centre. With his career over, Tallis leaves the elite firearms unit and is utterly disillusioned. A year later, Tallis is approached by a shadowy figure working for MI5. The offer is simple - unearth four illegal immigrants accidentally released from prison and hand them over to the authorities. The plan runs like clockwork, until Tallis makes an ugly discovery.