Someone else's house, someone else's apartment... Never before has Katya Petrovskaya, an employee of the press center of the Internal Affairs Directorate, been so lonely and so scared. But the operational situation requires that there be someone inside the huge house where the gloomy and seemingly senseless murders are taking place. A lot of facts have been collected, but they do not line up into a convincing version. Another murder, which occurred almost in front of Katya’s eyes, did not add clarity to this dark matter. And yet Katya feels that the answer lies in the powerful walls of the house, in its dark windows, gloomy staircases, in one dark day of the distant past...