When Simon Bowles commits suicide, no one is too terribly surprised. A graduate student at Cambridge University, Bowles had a long history of depression. But as Detective Sergeant Derek Smailes soon discovers, he also had a passion for investigating historical mysteries, and an extraordinary knack for solving them. His most recent project: uncovering the identity of the fabled “fifth man” in the notorious Cambridge spy-ring of the 1930s. Could Bowles possibly have solved that mystery? And could his solution – his “theorem” – have brought about his death? Rooted in the (thoroughly researched) history of the Cambridge Spies, The Cambridge Theorem will delight anyone for whom the name Kim Philby rings a bell, as well as readers of intelligent, tightly crafted espionage.