Investigation Bureau Quartet

Something mysterious is happening in the empty neighboring apartment. Suddenly, a closed piano starts playing classical music. Is there really a ghost in the apartment? Two best friends, Asya and Matilda, decide to get to the bottom of it. And now, some genuine thieves are trying to break into the house... How can they not call for help from their friends - Mitya and Kostya? After all, only together can they solve the mystery of the empty apartment and bring the wrongdoers to justice!