The case of the serial maniac is closed, investigator Mukaev has disappeared into thin air, and only his best friend Ruslan Svistunov has any idea what really happened. It’s obviously too early to put an end to this story. The house where Ivan Saransky’s underground laboratory was located burned down, but the notes of the talented chemist remained. Everyone understands perfectly well the value of his scientific research and experiments with human memory. The hunt begins for the invented Saransk medicine. The scientist's mistress Olga decides to make a lot of money from this and comes up with a cunning plan to get rich and disappear. But her plans are confused by a mysterious murder and the same Ruslan Svistunov, who is leading the investigation...