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.

Silvia grows up in miserable circumstances. Her father is an incurable drunk who neglects his family. His first daughter was stillborn, the second died at a young age, and the third was only eighteen when she went mad and died.

Hugo Writley, the son of an American shipping magnate, travels to Holland accompanied by his steward, Longway. On the night of their arrival they go to a cabaret, where they get into conversation with two men and their girlfriends who, at closing time, invite the Americans to their home for a few drinks. The hosts, however, turn out to be 'land-sharks' planning to strip the two inebriated Yankees of their cash.