"Silver Blaze", one of the 56 Sherlock Holmes short stories written by British author Sir Arthur Conan Doyle, is one of 12 in the cycle collected as The Memoirs of Sherlock Holmes. Doyle ranked "Silver Blaze" 13th in a list of his 19 favourite Sherlock Holmes stories.
One of the most popular Sherlock Holmes short stories, "Silver Blaze" focuses on the disappearance of the titular race horse (a famous winner) on the eve of an important race and on the apparent murder of its trainer, John Straker. The tale is distinguished by its atmospheric Dartmoor setting and late-Victorian sporting milieu. It also features some of Conan Doyle's most effective plotting, hinging on the "curious incident of the dog in the night-time:"
Gregory (Scotland Yard detective): "Is there any other point to which you would wish to draw my attention?"
Holmes: "To the curious incident of the dog in the night-time."
Gregory: "The dog did nothing in the night-time."
Holmes: "That was the curious incident."
Inspector Gregory has already arrested a man in connection with John Straker's murder by the time Holmes and Watson arrive at King's Pyland, the Dartmoor stable owned by Colonel Ross, from which Silver Blaze is missing. The suspect is Fitzroy Simpson, a London bookmaker who has come to Dartmoor (and specifically to King's Pyland) to gather information relating to his professional activities (which include wagers placed on favourites for the Wessex Cup, the race in which Silver Blaze is to run). However, to Holmes, from the outset, there seem to be a number of facts that do not fit the inspector's case against Simpson, damning as it looks. It seems odd, for instance, that he would lead the horse out on to the moor simply to injure or kill him. That could be done right in his stall. He could not have stolen the animal. What good would such a famous thoroughbred be to him? Why has an exhaustive search of the neighbourhood not turned up Silver Blaze? What has Simpson done with him?
Sherlock Holmes soon tracks down Silver Blaze, literally: his tracks (along with a man's) are clearly visible in the soil, albeit intermittently. Holmes also deduces why the police could not find the horse, despite having looked right at him. Holmes ensures Silver Blaze's safety, and turns his mind to other aspects of the case.
John Straker, Silver Blaze's late trainer, has been killed by a blow to the skull, presumably administered by Simpson with his "Penang lawyer," a clublike walking stick. Simpson's cravat is also found in Straker's hand, and the latter's coat is found draped over a furze bush. A knife is found at the crime scene—a peculiarly delicate-looking one, with a small blade. John Hamish Watson, from his medical experience, identifies it as a cataract knife (used in cataract surgery). Useful as it is for that purpose, it would be unsuitable as a weapon; in addition, Straker also seems to have stabbed himself in the leg with it.
One of the stable lads, Ned Hunter, was on guard duty the night of the crime, but he proves to have been drugged with powdered opium placed in his supper. No one else who ate the curried mutton made at the Strakers' house that evening suffered any ill effects, but Hunter was in a profound stupor well into the next day. Straker's pockets contained two interesting items: a tallow candle and a milliner's bill for (among other things) a 22-guinea dress, made out to one William Derbyshire. There is the curious incident with the dog, and a problem with the sheep kept at the stable: a shepherd tells Holmes that three of his animals have recently become suddenly lame.
Holmes's powers unravel the mystery, and lay bare what villainies there are to be exposed. He visits the milliner's shop in London and determines, using Straker's photograph, that Straker posed as Derbyshire. This establishes his motive: he had a mistress with expensive tastes, and tried to influence the race's outcome to earn himself a large sum of money.
The curried mutton was a clue, also; only such a spicy dish could have masked the taste of powdered opium, and it was impossible for Simpson to arrange a highly seasoned meal that evening for his purposes. Therefore, someone in the household must have conceived the idea—namely, Straker himself.
The "curious incident of the dog in the night-time" is easily explained: the dog made no noise, because no stranger was there. As Holmes explains: “I had grasped the significance of the silence of the dog, for one true inference invariably suggests others....Obviously the midnight visitor was someone whom the dog knew well. It was Straker who removed Silver Blaze from his stall and led him out on to the moor." Straker's purpose in doing this was to use the cataract knife to inflict a slight injury upon one of the horse's legs. He had thought to use Simpson's cravat (which the latter dropped when he was expelled from King's Pyland) as a sling to hold the horse's leg to cut it. But instead, Straker was killed when the horse, sensing that something was wrong, panicked and kicked the trainer in the head. The lame sheep had been used by Straker for practice.
Colonel Ross's main concern, of course, is getting his horse back safely. Holmes chooses not to tell Ross where his horse has been (although he has known all along) until after the Wessex Cup, which is won by Silver Blaze. At first the Colonel does not recognise his own horse, since the animal's distinguishing white markings have been covered with dye. Holmes then explains the details of the case step-by-step to the satisfaction of the Colonel, Watson, and Inspector Gregory.
Gregory is one of the more competent police detectives Holmes works with in the course of his career. He conducts a thorough investigation of the crime before Holmes's arrival, and gathers all the evidence Holmes needs to solve the case. Holmes notes that Gregory is "an extremely good officer," and observes that the only quality he lacks is imagination—the ability to imagine what might have happened on a given occasion, and act on this intuition.