Investigator Muromtsev is investigating the malfeasance of policeman Pozdnyakov. He on football figured out "for three" with two unknown people, after which he woke up in a sobering-up station without a certificate and without a weapon. It turned out that an unknown tranquilizer was mixed into his alcohol.
Metoproptizol is the name of the psychotropic drug that was used to poison the district police officer. Now the criminals are robbing apartments, presenting to the tenants a certificate stolen from a policeman. Investigator Muromtsev is trying to understand how the bandits are connected with the law-abiding professor Panafidin.
Muromtsev learns the terrible secret of Professor Panafidin. A few years ago, a colleague of the scientist Lyzhin invented a tranquilizer capable of revolutionizing psychiatry. The envious Panafidin removed Lyzhin from work, and he himself handed over the drug to the bandits.
Muromtsev is following Panafidin, trying to prove his involvement in burglaries. But most of all the investigator is now interested in Lyzhin. Who is he? Madman, perpetrator or victim? Meanwhile, another robbery takes place.
Muromtsev finds the robbers. Case is closed. Panafidin is not guilty. He committed another crime, but, alas, the investigator cannot punish him. The "case" of contemporary Mozart and Salieri - Lyzhin and Panafidin - cannot be "closed".