A timely shotgun blast from the Comte de Rougerac (alias Lupin) stops a train under which the beautiful Amélie is about to throw herself. Her only possession, a painting by Van Beuken, “La danseuse aux sabots”, has been stolen. The expert, Denger, having certified to the insurer, Blatt, that the painting was a copy, Amélie received only a ridiculous sum to compensate her for the theft. Lupin loves pretty women too much not to intervene in this dubious affair.

The famous American film writer Douglas Dutchman arrives in Germany aboard the Zeppelin. The press is there, as is the producer of his film, Siegfried Heidkamp, and the German star Brigitte Barett, who is to be his partner. After a triumphant welcome, Douglas Dutchman is invited to open an exhibition of jewelry belonging to Heidkamp's wife, Romy. During the rehearsal of the ceremony, Dutchman claims that the showpiece, the famous Ka-Hi-Dor diamond, is a fake. Everyone is stunned.

A beautiful woman at the wheel of a luxurious sports car... that's all it takes for Lupin to embark on a new adventure. Under the name Lutz Pindor, Count Pryberg-Artikoffen, of the Berlin Jockey Club, he travels to the splendid estate in the Bavarian Alps where Hélène (the pretty woman with the car) and her husband, Baron von Wiesenberg, have organized a horse-riding club. Lupin's arrival coincides with a macabre discovery: ride manager Hornung has just been murdered.