When Simon Bowles commits suicide, no one is surprised. After all, Bowles?a graduate student in mathematics at Cambridge University?had a long, well-documented 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 fans of intelligent, tightly crafted espionage.