Black Demon (2017)

Unremarkable at first glance, the murders in different parts of the city lead a young investigator named Sergei into a maze of dirty old secrets. For a long time, Sergei can't understand the motives or thought process of the criminal. But one detainee gives him a good hint: the scenario of the killer's actions inexplicably resembles the plot of the cartoon "About the Silly Winky-String", which is shown on TV in the city of N. The intrigue grows, and as the murders continue, the events take on an increasingly sinister tinge.