1927. Moscow. The heyday of NEP, cooperatives, trusts, theft, and fraud. Investigator Mezentsev from the provincial court office (gubsud), forensic expert Professor Grenikh, and trainee Petyа Vorobyov are sent to a house call to an apartment where a financial inspector and a runaway repeat offender are found dead. Both are buried under a layer of black foam, resembling coal-like smoke—sugar charred with sulfuric acid. The masked robber used hypnosis, getting into the apartment of an ordinary clerk. The owner and the murdered men had no connection to each other. But in the reporting documents of the district finance office, many economic violations are found—violations that were uncovered only because of this incident. Newspapers rush to declare the killer a folk avenger, but Grenikh suspects that not everything is explained so simply…