The text implements a peculiar approach to the well-known topic “Dostoevsky and existential philosophy”. The author introduces a metaphor, based on which, it seems possible to conceptually and laconically reconstruct the philosophical position of the Russian thinker and, at the same time, to explicate a number of paradigm features of existential ontology and epistemology. The main thing is in the appearance of another (perhaps not superfluous) dimension of understanding the human place in the world. “An underground man in a legal position” is the announced basic metaphor. It makes it possible to clarify the meaning of the idea of unconcealedness and concretizes the link of uniqueness and inconsistency, on which, characterizing a person, existentialism focuses on. A philosophical interpretation of the underground from the “Notes” of the same name written by F. M. Dostoevsky and, with reference to the novel «Demons», an interpretation of the vulgarized underground are given. The “method” of Dostoevsky, as far as it is generally correct to speak of such, is identified as existential dialectics.