In the spring of 1945 the Allies arrested the physicists they believed had worked on the German nuclear programme. Interned in an English country house owned by MI6, their conversations were secretly recorded. Operation Epsilon sought to determine how close Nazi Germany had come to building an atomic bomb. It was in this quiet setting - Farm Hall, near Cambridge - that the interned physicists first heard of the attack on Hiroshima. Aside from changing the course of history, that night was also one of great shock and personal defeat for the physicists - they were under the assumption that they alone had discovered nuclear fission. This is the story of Nazi Germany's hunt for a nuclear bomb and the genius, guilt and hubris of lauded, respected scientists.