A new investigation by the charismatic detective Vikenty Petrusenko, who has unique deductive abilities and knowledge, this time leads him to a mystery. Is it possible to explain the phenomenon of somnambulism? Especially if a healthy boy begins to walk and talk in his sleep. Just one detail: the baby is the heir to a huge fortune, and by chance he is taken care of by his dear, loving aunt, who dotes on him... Is a sudden illness a play of fate or an evil, insidious plan that even the luminaries of the underworld have never dreamed of? Petrusenko fearlessly stands up to protect the child, and during the course of the investigation he comes across mysteries worthy of the pen of Alexandre Dumas and Arthur Conan Doyle! And there is no doubt that they will all be revealed!