It is Midsummer, 1631, and while Alexander Seaton and his fellow masters enjoy the holiday, Robert Sim, librarian of Marischal College, is murdered in a dark alleyway in town. As the university and town authorities investigate the murder, Seaton is asked by the college principal to look into Sim's private life. During the course of this research, Alexander discovers a side to the librarian he could never have guessed, and personal feelings threaten to cloud his judgment and endanger his new marriage.

The fourth book in the highly acclaimed Alexander Seaton series. 1635: Europe is in the grip of the brutal territorial and religious struggle of the Thirty Years' War. Fear stalks the town of Aberdeen as a ship recruiting for the wars lies at anchor in the river mouth.

Captain Damian Seeker has gone north. Charged with preparing the way for the rule of the major generals, he is now under the command of Colonel Robert Lilburne at York. But when Lilburne orders him to a small village on the North York moors with details of the stringent new anti-Royalist laws, Seeker finds that what should be a routine visit will reveal a plot to rival anything in scheming London.

London, 1655, and Cromwell's regime is under threat from all sides. Damian Seeker, Captain of Cromwell's Guard, is all too aware of the danger facing Cromwell. Parliament resents his control of the army while the army resents his absolute power. In the East End of London, a group of religious fanatics plots rebellion. In the midst of all this, a stonemason uncovers a perfectly preserved body dressed in the robes of a Dominican friar, bricked up in a wall in the crumbling Black Friars.

London, 1654. Oliver Cromwell is at the height of his power and has declared himself Lord Protector. Yet he has many enemies at home and abroad. London is a complex web of spies and merchants, priests and soldiers, exiles and assassins. One of the web's most fearsome spiders is Damian Seeker, agent of the Lord Protector. No one knows where Seeker comes from, who his family is, or even his real name. All that is known of him for certain is that he is utterly loyal to Cromwell and that nothing can be long hidden from him.