Early in the morning on April 19, 1956, on a mission for MI6, Lionel “Buster” Crabb—the British spy who inspired Ian Fleming’s character James Bond—dove into the waters at Portsmouth Harbour and vanished. Stories began circulating that Crabb had been swimming near the Soviet cruiser Ordzhonikidze, which brought Nikita Khrushchev to the U.K. for a visit. But 67 years later—even though a body was found, possibly Crabb’s—the case remains cold and British papers remain mysteriously classified until 2057. In the podcast Cover Up: Ministry of Secrets, the historian Giles Milton takes listeners into both the case and Crabb’s world. “The disappearance of Lionel Crabb remains one of the last great secrets of the Cold War,” Milton wrote back in his 2015. He has not stopped thinking about it. —Clara Molot