Thanks to a rich dowry, Apollonia managed to arrange her destiny: she married teacher Andrei Khoroshevsky and together with him opened a boarding school for girls. A mysterious stranger tried to persuade them not to buy the house they had chosen for the gymnasium, but the couple, of course, did not listen to him. And, as it turned out, it was in vain: the boarding school students began to complain that a terrible dwarf scared them at night... But that was not all the troubles - suddenly Khoroshevsky disappeared! His relative, St. Petersburg police investigator Konstantin Serdyukov, an excellent analyst and heart expert, talked with the girls who hastily went home, and realized: the dwarf was not a figment of their imagination. Did he really kidnap Andrei?