The image of Sherlock Holmes in 'The Hound of the Baskervilles' is perhaps the most enduring image we have of him. You see, an Inverness cloak and deerstalker cap are inappropriate wardrobe for the town, and belong in the country. Sherlock Holmes is predominantly a city dweller and city investigator; it is relatively uncommon that he treks out on adventures, but the case of the mysterious death of Sir Charles Baskerville and the attempted murder of Sir Henry Baskerville led him to the Dartmoor plain. Thus, country garb was in order. This is where we get much of our imagery.
Also helping with this is that every major actor to play Holmes has considered 'Hound of the Baskervilles' to be the ultimate Holmes story to act -- rather like the Hamlet of Conan Doyle's work. Holmes was a popular film icon, and in the early decades of the twentieth century several dozen films were made of Holmes, but the first after these many films to be set in Victorian times (and not be updated for the screen) was a version of Hound. Ellie Norwood, Basil Rathbone, Peter Cushing, Jeremy Brett -- many distinguished actors have considered this among their greatest roles.
Watson dates the case to 1889, but various reading authorities, knowing the good doctor's occasional attempts to distort details to protect the privacy of the innocent, have dated this to between 1886 and 1900.
In fact, the novel appeared in serialised form in the Strand magazine, the great first-publication site of most Holmesian tales, between August 1901 and April 1902, after Conan Doyle had attempted to kill off the great detective in the short story The Final Problem, which showcased Holmes' battle with Moriarity, the Napoleon of Crime. In fact, Conan Doyle came to dislike the character of Holmes because it was a distraction to his other pursuits.
So, bowing to public pressure, Conan Doyle penned Hound of the Baskervilles to placate the public demand for more stories, but took care to place it before the death of Holmes, in the hopes that he could leave the detective safely dead (if not buried). Such was not to be, and we find a few years later that in fact Conan Doyle 'resurrects' Holmes in a rather ingenious fashion.
But, on to the story at hand. Holmes and Watson, at home at 221b Baker Street, are approached by a Dr. James Mortimer regarding the death of Sir Charles Baskerville and a family curse which involved evil forces in the form of a satanic hound. Mortimer is concerned for the safety of the new proprietor of the family lands, freshly arriving from Canada, who had a new boot stolen, then an old boot stolen, in his hotel in London. Later Holmes would put together the significance of this seeming strange minor act (no, I won't tell you).
Holmes sends Baskerville and Watson together to the country estate while he tends things in London on another case. In reality, Holmes is setting Watson up as a diversion, while he investigates the moor and the surroundings of the Baskerville estate under cover. Life at the estate is a bit strained, given the murder, an attempted murder, a curse, and all. The neighbours seem nice enough, though. Or are they? Watson picks up on curious little details of their relationship, which he reports back in written notes to Holmes (which have been redirected to his moor outpost).
Eventually Holmes reveals himself to Watson, and then to Baskerville, and the chase is on in earnest, to discover the reality of the mysterious creature each have seen or heard. In good mystery fashion, we come across long lost relatives and an inheritance to be had; we find plots and subplots muddied by superstitious belief and fear, on a mysterious plain in southwestern England.
All the elements combined that are now considered standard bits for a well-done country English mystery. But the mystery does not stop merely with the story. In true mystery fashion, appearing in the Daily Express edition of March 16, 1959, there were doubts cast upon the authorship of Hound of the Baskervilles. The one who carried the dispute was named none other than Baskerville, Harry Baskerville. He credited the story to one Fletcher Robinson, who died (perhaps of the Egyptian mummy's curse) at age 35 shortly after the publication of Hound. With his death, only Baskerville remembered the issue of co-authorship. Baskerville claims it was Robinson who 'borrowed' the Baskerville name.
One of Conan Doyle's heirs, Adrian Conan Doyle, heatedly denied involvement of Robinson past possible 'conversations' that might have taken place between Arthur Conan Doyle and Robinson. But, he did not deny Conan Doyle's possible 'inspiration' from Robinson.
One Baker Street Irregular (an exclusive club of Holmesian experts) was doing a monograph on this issue as well, claiming that the reason why Holmes appears so infrequently is due to the fact that he had to be written in to an otherwise essentially completed story. This Irregular travelled to meet with Baskerville, and hinted at discoveries he had found. But alas, the Irregular died three weeks later in America, his monograph never published and his notes were never found. Perhaps a dog ate the homework? A mysterious hound, perhaps?