A mass brawl at a metro station that ruined the lives of five passengers, the inexplicable death of a psychology professor and a daring robbery of a thrift store. Each time, going to a crime scene, the investigative team finds a mysterious symbol left by the hand of an unknown criminal. There are no witnesses, but surveillance cameras capture a man whose face is hidden under a mask. The head of the investigative department, Sergei Fedotov, begins the investigation without any additional information, but the deeper he studies the details of the crimes, the stronger his confidence that there is no ordinary criminal hiding under the mask.