Meanwhile, Leo returns from America and asks his father permission to see Annie again. Jan asks Van Haaften for a loan, but Vaan Haaften deems his experiments as silly and fires him. Jan almost wants to give up, when in the park he stumbles on the fortune of a dead man who has committed suicide. The included letter states 'finders keepers'. From this money, he can finally buy platina and continue his experiments. In the meantime, Van Haaften's factory has gone out of business. Van Haaften cannot cope with this setback and during the night he commits suicide in his office. During the same night, cousin Willem has broken into the factory in a bid to find out more about the secret of Delft. He sees the lifeless body of Van Haaften, but does not raise the alarm. Instead, he takes the remaining 3,000 gulden belonging to the factory which he finds in Van Haaften's pockets and he also pinches his suicide note. The next morning Jan finds the body. He calls in for help, but the police now suspect him of committing murder. He is considered to be the main suspect because he has a lot of money on his person and a some money went missing at the factory, and is arrested. Right before being taken to the police station, he hands over the secret Delft formula to his daughter Lilly. Some time later Leo Van Haaften has taken over his father's position. In place of Jan, fraudulent cousin Willem is hired as the new factory manager and is still trying to find out the Delft secret. He discovers that Annie is now the owner of the formula and tries to persuade her to give him the formula, but she is more concerned with her and Leo's relationship. They would love to get married but are not allowed to as her father is in prison. In the ensuing trial, Jan is charged with the murder of Van Haaften with a demanded sentence of 20 years imprisonment. Eventually he is found guilty and sentenced to ten years imprisonment. In the meantime, Willem uses force to try and get his hands on the formula. He repeatedly pesters Lily, but she learns the formula by heart and burns the paper on which it is written. The situation gets out of hand and her house burns down to the ground. She finds new accommodation at her sister Annie's house, but is still being harassed by Willem. She writes a mock formula and makes sure that he finds this fake copy. Willem struggles with the experiments, meanwhile Lily's father gives her the task to find the letter written by the person who had committed suicide in the park.