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 t...