The news spreads across Saint-Marco about the death of the alchemist Adeamus, who, according to rumors, created the philosopher's stone and learned to turn any metal into gold. The alchemist's alarmed patrons, who donated considerable sums of money for his research, turn to Baron de Segur with a request to investigate the death of Adeamus, and at the same time look in his house for the coveted recipe for the philosopher's stone. Mark is not too interested in this matter, however, he still has to take it on by order of the king, who is concerned about the possible violation of the royal monopoly on gold mining. Arriving at the alchemist's house, Mark notices that his servants are clearly not who they say they are, and in the laboratory he finds a strange piece of paper with secret writings, for which a real hunt soon begins.