Holmes’s hyperosmia, or unusually acute sense of smell, is an invaluable detective ability. Throughout the text, it allows him to quickly solve mysteries that otherwise might have dragged on: In the novel’s early chapters, his sense of smell directs them straight to Sloane Stone’s body; later, in the Siglik house, he is able to smell the pit of bodies even through layers of stone and concrete, despite being unconscious from a heroin overdose mere moments before. Holmes’s hyperosmia therefore takes on a near-magical power, one that enables the text to move forward quickly in perpetual action without the slower pace of logical deduction (which the original Sherlock Holmes was best known for performing).

Holmes’s sense of smell also leads him to one of his greatest struggles in the text: his heroin use. Holmes frames taking the drug as a reaction to the intense and constant sensory barrage of his hyperosmia; his choice to consume heroin through the nose makes him both worried and faintly hopeful that his sense of smell will be dulled. His decision to attend drug rehabilitation at the end of the novel suggests that he no longer wishes to compromise his sense of smell via heroin.