1986 Siberia. A company of young artists organized a festive feast. The evening promised to be bright: the guys and girls were obsessed with creativity, cheerful, in love with each other... But in the midst of the holiday, a tragedy happened: the owner of the apartment was found in the next room with a knife in her chest. Investigator Andrei Laptev has no doubt: the killer is one of the party participants, because there were no strangers in the apartment. But who committed such a terrible crime? Laptev decides to reconstruct the events of the ill-fated evening, hoping to identify the killer with the help of one inconspicuous detail...