Autumn 1829, Smolensk province. The local landowner Prince Seversky is having a wedding! A hospitable home, a festive table, colorful fireworks - it would seem that nothing foreshadows trouble. But fate decrees otherwise... In the morning, after a magnificent celebration, the prince is found dead in his bed, but in his arms is not the newlywed, but his mistress Nastya! The main version of death is carbon monoxide poisoning. There is a whole estate of volunteer “detectives”: they get in the way, interfere with every step. And most of all - doctor from St. Petersburg Ilya Andreevich Tonner, who has a completely different version of what happened...