In Chapter 14, Watson personifies the Grimpen Mire as he describes trying to navigate through it with Holmes:
Its tenacious grip plucked at our heels as we walked, and when we sank into it it was as if some malignant hand was tugging us down into those obscene depths, so grim and purposeful was the clutch in which it held us.
The Grimpen Mire, part of the Moor, is a treacherous swampland filled with quicksand-like marshes. Jack Stapleton refers to it early on as “a bad place” and Watson later observes the Mire swallow a wild pony whole. Stapleton, a trained botanist, claims to be the only person on the Moor capable of navigating the Grimpen Mire after spending time there observing its plants and insects. When Watson and Holmes are forced to navigate through it, following Stapleton’s footsteps, the force of the quicksand is so strong it appears supernatural, as if it has a mind of its own, with an intent to capture Watson and Holmes. Watson and Holmes are only able to get through the Mire safely because they follow Stapleton’s exact footsteps. However, unable to find or capture Stapleton because of the fog, later on Watson and Holmes deduce that Stapleton eventually met his death by drowning in the deathly swamps of the Grimpen Mire.
Like the rest of the Moors, the Grimpen Mire represents the world of the supernatural, full of the abnormal, mystical, and odd. It is where the infamous Hound of Baskerville supposedly appears, frightening Sir Charles Baskerville to death. Because the Mire and Moor are shrouded in mystery, Stapleton is able to exploit this fear of the supernatural and commit his crimes. Through Stapleton’s act, Doyle explores the idea that humans have a tendency to attribute the inexplicable to the supernatural.