In The Flying Crusaders, Joseph Silberman was an American who was a house guest of Sir Giles Mancroft during the incident in August 1939 when the valuable painting "The Flying Crusader" had gone missing. Silberman claimed to have fought in the Escadrille Lafayette during the First World War and had been invited to a party at Mancroft Castle given by Sir Giles to show off his collection of vintage aircraft. During the night, Silberman had been involved in a scuffle with Sir Giles' butler, Smithers, in the hangar where the old aircraft were kept. According to Silberman, he had gone down to the library and noticed that the painting "The Flying Crusader" had been cut from its frame. He saw a light in the hangar and had gone to investigate. There, the butler had attacked him. The ensuing fight was so violent that the butler sustained a severe head injury and died without recovering consciousness. Silberman himself was found injured and leaning against the "Flying Crusader" aircraft. He was hospitalizd for some time and told police that he thought the butler had taken the painting and was trying to make off with it.
After the Second World War, Silberman had, for some reason, become wanted by the Anti-American Activities Committee and was hiding out in the Soviet sector of Berlin. He met a US Air Force sergeant named Galton and persuaded him to travel to Mancroft Castle to buy the "Flying Crusader" aircraft which was being auctioned off by Sir Giles. Galton was supposed to buy the aircraft and deliver it to [[[Hookley Green]] nearby where Silberman would collect it. It turned out that Silberman had stolen the painting and had hidden it inside the aircraft.
Silberman's scheme did not succeed due to Biggles' intervention. The butler's son was a mechanic who served under Biggles during the war and he requested that Biggles clear his father's name. Silberman was arrested and subsequently hanged, although the story did not make clear whether this was by British authorities for the murder of the butler at Mancroft Castle, or by the Americans for treason.