Dirk Janse

After years of touring abroad with his "Cirque Hollandais", Hendrik van Dalen returns to Holland, hoping that his brother will lend him financial support. Since the death of his wife, things have gone from bad to worse with Hendrik, who drowns his sorrow in drink. Moreover, he has set his heart on the circus-equestrienne, who pretends to love him but is having an affair with the company's wrestler. By encouraging Hendrik to drink, they hope to get their hands on his possessions. Hendrik's daughter sees through their designs and, with the aid of the clown Louisot, tries to foil their plans.

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.