Special Branch receives a chilling tip-off about suspected terrorists being in possession of something which will 'finally bring London to its knees'. But the individuals concerned have disappeared off the map, and DS Robert McGraw finds himself up against an unseen and ruthless enemy who will stop at nothing to further their cause. Along the way, McGraw discovers a plan that will kill hundreds if it succeeds.

Concurrently, Sally Taylor is writing an article about a 'shoot-to-kill' strategy, said to have been approved at the very highest levels, being pursued against the IRA by a small, elite team of British soldiers in the early seventies. What she discovers, with its attendant implications, will have a knock-on effect on McGraw.