Van Duylen, representative of a diamond syndicate, brings to Amsterdam the Koh-I-Noor II , the largest diamond ever found. In one of the city's oldest diamond-cutting establishments it is cleft and the nine small stones are polished. Escorted by detectives, Van Duylen takes the stones home and puts them in his burglar-proof safe. He tells his wife that its doors are electrically charged and that anyone opening them in the wrong way will immediately be electrocuted. Two suspicious persons, Jack the Acrobat and the lion-tamer Feenstra, prowl around Van Duylen's villa, inspecting the doors and windows.