It is Midsummer 1631. While Alexander Seaton & his fellow masters enjoy the holiday with their students Robert Sim librarian of Marischal College is murdered in a dark alleyway in town. While the university & town authorities investigate the murder Seaton is asked by the college principal to look into Sims private life. In the course of an investigation in which his personal feelings threaten to cloud his judgement & endanger his young marriage to Sarah he discovers a side to the librarian he could never have guessed at. It is only when a second apparently unrelated murder comes to light that Seaton begins to piece together the connections between a young weaver a consignment of books & events in a college in the Low Countries in order to unmask the perpetrator of the years-old deception that led to the two deaths.