Schmidt, scientific director of the Institute of Ethnography, enlists the detectives. His colleague, an expert on Old Slavic pagan cults, was killed during a robbery at his dacha. Schmidt asks to find a statuette stolen by robbers, the so-called Bryusov mermaid. Makar and Sergey begin an investigation and almost immediately come to the conclusion that the mermaid's abduction was not spontaneous.

A witness to the murder of Silbert, a young man living next door, is called up for identification by the morgue. The neighbor identifies killers Zilbert. It would seem that this fact should greatly facilitate the task of our heroes. But Makar rather quickly manages to catch the witness in a lie, and now all the threads of the investigation are lost.

Makar arrives in the village of Omuty near Rybinsk and finds out that the alleged killers are the Skovorod brothers. The mermaid that the brothers hunted for turned out to be a simple piece of wood created by a local woodcarver. Superstitious residents believe that a mermaid not only fulfills desires, but also endows its owner with a curse.