Richard Pokora is a talented young scientist who has won a prestigious award as a student. Therefore, he has the opportunity to continue working on his scientific discoveries in a major research center in Paris. He experiences contradictory moments there - he can work with the largest expert on the same problem, genetic influence of agricultural crops, but at the same time experiences loneliness. Only one friend he has from childhood is trying to distract his thoughts. In her free time, humility goes to Notre Dame and writes her diary. Even in French to practice in language. Life and mainly work are disrupted by anonymous threats that he has already received in Prague, but in Paris it continues. He ignores too much, trying to focus on research. After a few months, when they are already at the end of the research, there will be a tragedy. Professor Calbot is murdered and the murderer and humility will perish on the same day. It turns out that death was caused by an unknown sharp -poisoned substance from the Amazon. A complicated search for a murderer, who will be needed not only in Paris, but also in Prague. And so Paris criminals from the Goldsmiths, Commissioner Morelon and Inspector Maigret, as well as in Prague, the criminal Council Hladík and his Mordpart, appears on the scene. It shows how hard it is to look for a murderer who is a fanatical supporter of his perverted idea.