A series of gruesome killings take place in Dubai, Ghana and America. The victims are all connected with the SAS.

In Hereford Danny Black realises they have something more specific in common - they were all involved in training a young Muslim soldier, Ibrahim Khan.

Khan has been working under cover in Islamic State in a mission organised by MI6. Danny Black sets out to track him down with the help of Khan's MI6 handler on a trail that leads him to a library of ancient manuscripts in Damascus, the Syrian desert and finally back in the Brecon Beacons.

There Danny discovers that he has finally met his match, his deadliest enemy - and it is the last person he ever expected.