In Chapter 3, after describing the hound’s gigantic footprints, the story uses visual imagery to describe Holmes’s reaction:
[Holmes] leaned forward in his excitement and his eyes had the hard, dry glitter which shot from them when he was keenly interested.
The story focuses on the quality of light in Holmes’s eyes, which is described specifically and purposefully. Rather than using an adjective, for example “glistening” or “shining,” Doyle suggests that Holmes’s eyes are like a diamond, an association that emphasizes Holmes’s intelligence. Though Holmes is excited, the "hard, dry glitter" is not simply an expression of emotion, but of rational intelligence—it signals that he is "keenly interested," that his intellect is fully engaged in the case at hand.
Sherlock Holmes, as a character, is known for his brilliance of mind and reason, so much so that his name becomes a cultural reference to describe those who are unusually perceptive. In Holmes, Doyle creates a character who embodies a belief in the power and rationality of science. Holmes’s reliance on reason—rather than fallible emotion—allows him to solve mysteries, especially those with seemingly non-rational, supernatural causes like the Hound of Baskerville. Imagery like Holmes's glittering eyes helps impress on readers Holmes's reason-based abilities.
In Chapter 6, Watson uses rich visual imagery when he describes his, Dr. Mortimer's, and Sir Henry’s descent towards Baskerville Hall:
We had left the fertile country behind and beneath us. We looked back on it now, the slanting rays of a low sun turning the streams to threads of gold and glowing on the red earth new turned by the plough and the broad tangle of the woodlands. The road in front of us grew bleaker and wilder over huge russet and olive slopes, sprinkled with giant boulders.
The road to Baskerville contains many stages. Overall, the scenery shifts from a dense, urban enclave to a sparsely populated, rural landscape. This change in environment symbolizes a transition from the orderly, safe, and peaceful world of reason—represented by London, where Holmes and Watson are based—to the impenetrable, treacherous, and untamed world of mystery and superstition at Baskerville Hall. As the trio travel deeper into Devonshire County, a sense of foreboding and danger begins to take over the narrative. Behind them, the “fertile country” glows alluringly. As Watson looks ahead, however, the path seems darker, less contained.
This moment in the story also represents a shift in the narrative. From this point forward, the novel’s mood grows increasingly melancholy and bleak and is full of dark, picturesque imagery. The unruliness of the Moor, where Baskerville Hall is located, contains many supernatural notions—ghosts and devilish hounds, for example. The vastness of the moors also allows for a level of secrecy hard to attain in bustling, cramped London. When Holmes and Watson discover they are being followed in London, they discover it immediately. In comparison, both the escaped murderer Selden and an undercover Holmes are able to roam the moors undetected for weeks.
In Chapter 14, Watson uses fiery imagery when he and Holmes finally lay eyes on the infamous hound of Baskerville:
A hound it was, an enormous coal-black hound, but not such a hound as mortal eyes have ever seen. Fire burst from its open mouth, its eyes glowed with a smouldering glare, its muzzle and hackles and dewlap were outlined in flickering flame. Never in the delirious dream of a disordered brain could anything more savage, more appalling, more hellish, be conceived than that dark form.
Imagery is descriptive language that engages the human senses, in this case visual. The hound is immediately described in supernatural terms, beyond the realm of the “mortal” or living. The hound’s eyes and body have an exaggerated, dramatic quality, not unlike a nightmare. Indeed, Watson describes the vision of the hound as akin to a bad dream, unnatural and terrifying. The image of the hound appearing is the climax of the story; Holmes and Watson finally see the mysterious, other-worldly hound. Legend becomes reality, and as Holmes foreshadows in Chapter 3, they find out that the “Devil’s agents” are indeed made of “flesh and blood.” Fact and fiction meet. Superstition becomes fact. The story uses vivid, frightening imagery to suspend both characters and readers in this moment, until the mystery is resolved and the apparently supernatural hound turns out to be just a dog that Stapleton has painted with phosphorus to conceal his very human crimes.
