In The Unknown Diamonds, Shultz was the brother of Dr. Shultz, a German research scientist who maintained a research station in the deserts of Southwest Africa (now Namibia). The brother Shultz lived in Britain and would receive shipments of live monkeys sent by Dr. Shultz from Southwest Africa which had diamonds surgically implanted under their skins. Shultz would sell these diamonds and hand the money to a charitable institution in Germany which cared for disabled ex-soldiers.
This diamond smuggling scheme came to light when Shultz's house in Britain was burgled and some diamonds stolen. The diamonds were subsequently discovered during a police raid in the safe of a pawnbroker who was suspected of dealing in stolen property. The diamonds were identified as coming from Southwest Africa and Biggles was assigned to investigate how they entered the country.
Shultz was arrested at London Airport when receiving a monkey and decided to make a full confession to the police. In view of the charitable use he made of the proceeds and the fact that he lost his diamonds, the courts took a lenient view and he got off with a fine.