The suicide of Simon Bowles looks open-and-shut: He left a note, he had a history of depression. But as Sergeant Derick Smailes discovers, he also had a surprising ability to solve historical mysteries. His most recent project: Uncovering the identity of the fabled “fifth man” in the Cambridge spy ring of the 1930s. Could his solution—his theorem—have brought about his death?

“Few can rival this extraordinary novel” (West Coast Review of Books) about a contemporary cop who happens on a crime involving the Cambridge spy ring of the 1930s.