Did the 19th century German mathematician Bernhard Riemann discover more about the intricacies of prime numbers than he published? Did a notebook survive the clear-out of his papers following his sudden death in Italy? Could this notebook enable the breaking of 21st century internet security? Part biography, part thriller, The Riemann Notebook is the story of the search for a lost notebook and the secrets it may contain by two idealistic academics and by international security organisations with conflicting motivations.