At last the dashing courtier, Sir Robert Carey, has his precious warrant as Deputy Warden. However, his lethal henchman, Sergeant Dodd, is enraged with him for not massacring Dodd’s blood-enemies, the Elliots, at the incident at Dick of Dryhope’s tower.

And there is some kind of plot maturing in Scotland, something threatening the King of Scotland’s life. Carey rides to Edinburgh with Dodd and along with him, a mysterious tooth-drawer and philosopher, Simon Anricks. Mr Anricks has been invited to court by King James who is eager to hear him speak at a grand Disputation between the Ptolemaic and Copernican systems for the arrangement of the Sun and planets. Anricks plans to use mathematics in his speech.

At the dissolute and violent Scottish court, Carey has to keep an eye on Dodd, who may have taken money to kill him, help Anricks write his speech and work out how the King is supposed to die. Can he stop the assassination of the King?