When Simon Bowles commits suicide, no one is surprised. A graduate student in mathematics at Cambridge University, Bowles 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? Described by the Austin American Statesman as cross between "P.D. James and John le Carré," and combining a police procedural and a complex espionage yarn, the novel works equally well for fans of espionage (le Carré and Eric Ambler), and fans of the kind of police procedurals (Pascoe and Dalziel, say) where the characters come jumping off the page.