Once, in the middle of the night, graduate student Sashenka, her best friend Lyuska, Uncle Lyuska, the eccentric policeman Venya, the Moldovan trader Lyubasha, the Tajik janitor Ravshan and the surgeon Arkady gathered in the middle of the night in a dashing communal apartment... That same night Arkady decided to rent it out to the bandit Sena Pupu is a mysterious medical device, and in the morning Senya Pup was found murdered. District police officer Sviridov and investigator Kozelok just shrug their shoulders. Arkady is accused of stealing the device and threatens to fire him from his job. Lyuska and Sashenka decide to help the poor fellow by starting their own investigation into what happened. There is only one question: to whom and why was it necessary to not only kill Senya, but also steal a completely incomprehensible device? There are many possibilities. It's worse with motives...