Mavis Keeves is the daughter of a man who is ruined and dies as a result of reckless speculation, encouraged by Sir Harry Winderbank.

The wealthy De Roquevilles, the family of alcoholic veteran Jean Laurent, and that of farmer Godard; all have to deal with the outbreak of the Great War. To complicate things even more, Godard's daughter Anny falls in love with young Mario Laurent, who turns out to have inherited some of his father's vices. First part of Maurits Binger's epic silent trilogy.

Anny helps Mario escape from prison after his attempted murder of Gaston de Roqueville, who is now married to Ninette. Banker Sorga, an enemy spy, attempts to steal Mario's latest invention: a powerful explosive that could alter the course of the war. Second part of Maurits Binger's epic trilogy, now considered lost.

The happy life of Sylvia and Pieter is disrupted when Sylvia loses her sight and her sister Lyda falls in love with her husband.

Married housewife Alda decides to become a singer under the stage name 'La Renzoni', in a duo-act with her father. All goes well, until her husband mistakes her father for her lover...

When self-made businessman Pancras Duif decides to marry his much younger housekeeper, his entire family protests; eager to protect the family capital, sons Henk, Jan and Toon enlist a psychiatrist for help. The film is considered lost.

When his granddaughter is born, debt-ridden Colonel von Zwenken misses out on Aunt Roselaar's allowance of 20,000 guilders. Anxious to keep the money, his son-in-law telegraphs the aunt that a son was born, Frans, and the girl is brought up as a boy. Based on the novel by Anna L.G. Bosboom-Toussaint.

The secret from the title is the lost recipe for shiny Delft pottery, that Jan Vogel is desperately trying to rediscover. For his attempts he needs platinum, but the funds run out because the factory owner Van Haaften has lost his money in stock-speculations. Luckily for Jan, he finds a farewell letter in the park, including a large sum of money. Meanwhile, the owner's son Leo confesses his love for Jan's daughter Annie, but Van Haaften forbids their marriage.

Lona, a young woman who has no memories of her past, has been adopted by the rich industrialist Van Haaften. She is loved by Henri van Rhenen, a neighbour whose mother still mourns the loss of her daughter, who disappeared twenty years ago under mysterious circumstances. Lona has another suitor, Frans van Borselen, who hopes to marry her so that he can pay his gambling debts with her foster-father's money. Van Haaften discovers that Frans has been cheating at cards and offers him a revolver so that he can end his life honourably.

Kate van Marlen is blissfully happy with her partner, Count Alfred van der Loo. However, he has no serious plans for her and says he will never marry her. The young, spirited cavalry lieutenant Count Ruprecht van Halden thinks differently: for him, Lady Kate is the ideal woman. He courts the young girl and asks for her hand in marriage. Kate makes one last attempt to win Alfred over. During a garden party, she confesses her love to him once again, but Alfred refuses.