1593: Sir Robert Carey has been tasked by the King of Scotland with finding and killing the young engineer calling himself Jonathan Hepburn. There have been two dangerous attempts on King James's life within two days over the New Year, and Hepburn is at the back of both of them. Not to mention that the troublesome Catholic Earls have been doing deals with the King of Spain again, planning to bring Spanish troops to the West Coast of Scotland and march them into England.
Carey is willing to run Hepburn to earth in his home town of Keswick in Cumberland - the Lake District - but killing him will be difficult. He's clever and ruthless and enjoys murder. His family are the skillful and respectable Hochstetters, German miners who have been mining the hills for decades on behalf of Queen Elizabeth. They insist that Hepburn/Hochstetter is innocent.
Worse, Carey finds that his nerve isn't what it was since the events in Dumfries in the summer of 1592. He struggles to overcome his strange terror of the darkness of the mines. Hepburn knows the shafts and tunnels well and that's where he takes refuge.