The notion of "metaphysical detective fiction" (MDF) may seem something of an oxymoron. Where metaphysics is concerned with abstract concepts and deals with fundamental questions about being and knowing, detective fiction is regarded as an intrinsically unserious literary form, a "literature of escape", whose interest lies primarily in empirical clues and hard facts. However a brief look at the pool of authors of MDF leaves no ambiguity as to the fertility of this seemingly unnatural union. From Chesterton's Father Brown stories to Borges's Fictions and Nabokov's Pale Fire and closer to us, Eco's The Name of The Rose, it seems that detective fiction, with its interest for the ratiocinative process, has lent itself rather well, more specifically, to epistemological questions: what, if anything, can we know? What, if anything, is real? Within this frame, semiotic concerns take on a specific fictional role. These are fictionalised, mainly through unreliable, ambiguous or truncated texts (letter, notes etc), to introduce epistemological puzzles. Through this and other devices (like parody or subversion), MDF challenges the conventions of the genre, such as narrative closure (some crimes remain unsolved) and the detective's role as surrogate reader. Instead, MDF explicitly speculates about the workings of language, the structure of a narrative and the nature of reading. What matters is no longer the enigma, but the code or the method to solve the puzzle. Thus, in staging the difficulty of deciphering texts and of meaning-making, MDF also questions philosophical systems contaminated by the fictional desire of closure: how to understand the clues supposed to lead to truth while resisting the temptation of incorporating them into a system that verges on fiction? This paper aims to take a glimpse at this highly self-reflexive genre through a cross study of G.K. Chesterton's "The Wrong Shape" and "The Honour of Israel Gow" and J.L. Borges's "Death and The Compass".