Het geheim van Delft
Jan Vogel, foreman at the Van Haaften pottery, is busy with a new process for painting porcelain, but so far his experiments have failed. His employer, also in financial difficulties, cannot give him more money. Van Haaften objects to the relationship between his son Leo and Jan's daughter Annie. Jan promises to try to keep them apart. Annie, who earns a living playing the piano in a cabaret, is pestered by her cousin Willem, a rascal whom Vogel has dismissed from the factory and who wants revenge. Willem overhears Annie's sister Lilly saying that when father's formula is a success they will be rich. His greed aroused, he wants to get hold of the secret. Even without Van Haaften's help, Jan continues his experiments. Going to the factory one night, he sees Willem hanging around. Jan warns his employer and advises him to buy a revolver. Later, while taking a walk, Jan finds a wallet containing 2000 guilders and a note from the owner saying that he has taken his life and the money is for the finder. With it Jan buys what he needs for his work. In his office that evening, Van Haaften, whose speculations have been unfortunate, asks himself what good are the 2000 guilders he has when he needs 50,000. He throws the money on to a table, writes a farewell letter to his wife and shoots himself. Willem, sneaking into the factory, hears the shot. He pockets the banknotes, hoping that Jan will be accused of theft and murder. Jan works all night and, on opening the oven with a painted vase, sees that his process is a success. Hurrying to the office to report to Van Haaften, he is shocked when he sees the body. As his story of finding money is not believed, Vogel is arrested and sent to prison. Before being taken away, he gives his formula to Lilly. Willem, re-employed by Leo, now chases Lilly, who finally gives him a formula, but it is only a copy in which she has made some alterations. Naturally, Willem's experiments fail. When he sees Lilly give the real formula to Annie he pursues her, not only with his declarations of love but also to get hold of the secret. Fearing for her life, Annie runs away and seeks refuge in a windmill where Willem finds her. At her wit's end, Annie climbs onto one of the sails. When Willem follows, the rope fastening the sails gets detached. The sails start turning and Willem is mortally wounded. Before Annie is rescued she makes a number of revolutions while clinging to the sail. In the meantime, Lilly has found information about the man who committed suicide shortly before Van Haaften's death. At an auction she buys the suicide's blotting-book, on the last page of which there is a copy - in mirror writing - of the letter her father had lost. Because of this evidence, Vogel's trial is revised and he is acquitted. As Vogel's invention will bring prosperity to the factory, Leo appoints his future father-in-law as his business partner. Shortly thereafter the engagement of Annie and Leo is celebrated.
Minny van Haaften, Leo's sister
Leo van Haaften
Mrs. Van Haaften
G. Donaldson, Of Joy and Sorrow. A Filmography of Dutch Silent Fiction, Amsterdam (1997), p. 158