The article demonstrates how the attempt to create the “realistic detective novel” destroys the basis of the detective genre. The theoretical foundation of the research is the works by Nikolay Volsky, devoted to the theory of detective story. The materials of analysis are the works of Dorothy Sayers (“Clouds of Witness”) and Josephine Tey (“The Franchise Affair” and “The Daughter of Time”). These writers join elements of the detective poetics (first of all, the detective mystery) with the elements of the realistic style (realistic characters and type of narrative), and that connection results in clash between style and genre. The detective mystery becomes less distinct, Sayers and Tey highlight not puzzle, but people, i.e. the structure of the genre falls to ruin. We also notice the realistic solution in “Clouds of witness” by Dorothy Sayers as well as the little convenience of such solution (indicated already by S.S. Van Dine).