Frank Close, OBE, is Professor of Physics at Oxford University and a Fellow of Exeter College. He was formerly Vice President of the British Association for Advancement of Science and Head of the Theoretical Physics Division at Rutherford Appleton Laboratory. He is the author of more than 200 research papers and two-time winner of the Association of British Science Writers award.

The memo landed on Kim Philby's desk in Washington, DC, in July 1950. Three months later, Bruno Pontecorvo, a physicist at Harwell, Britain's atomic energy lab, disappeared without a trace. When he re-surfaced six years later, he was on the other side of the Iron Curtain.

One of the most brilliant scientists of his generation, Pontecorvo was privy to many secrets: he had worked on the Anglo-Canadian arm of the Manhattan Project, and quietly discovered a way to find the uranium coveted by nuclear powers. Yet when he disappeared MI5 insisted he was not a threat. Now, based on unprecedented access to archives, letters, surviving family members and scientists, award-winning writer and physics professor Frank Close exposes the truth about a man irrevocably marked by the advent of the atomic age and the Cold War.