“A Scandal in Bohemia” (1891)
This story owes a clear debt to Poe's "Purloined Letter." In it, the King of Bohemia asks Holmes to help him get some compromising photographs of him and Irene Adler--an America opera singer whom he met in Warsaw where she was prima donna and with whom he once has a secret liaison. Now that he his preparing to marry a diplomatic Scandinavian princess, he can't afford to have those photographs out and about and he thinks that Irene will blackmail him with them. Holmes manages to find out where the photographs are by playing a trick on Adler: he disguises himself as clergymen, is beat up, takes refuge in her house, has Watson toss in a smoke rocket, and tricks her into believing that he house is on fire, after which, on cue, she rushes to preserve her most prized possession, the photograph of her and the King of Bohemia, which she conceals in a secret panel behind the bell pull. But Adler immediately suspects she has been tricked, and denies a trick of her own: she leaves Britain the following morning with her financee and puts a photograph of herself in place of the other photograph of her and the King. This is what Holmes finds, and he finds himself beaten by a "woman's wit." Irene claims that she never intended to blackmail the king and kept the photo only for her protection, although she was very badly used by him, as he promised to marry her and then abandoned her. Holmes asks for the photograph of Irene as a reward for his trouble.
“The Red-Headed League” (1891)
In which the London criminal John Clay attempts to rob a bank (freshly infused with a shipment of French gold coins) by devising the following elaborate scheme: by getting a job in the London Pawn shop next to the bank in question under the alias of Vincent Spaulding and luring his employer--the red-headed Jabez Wilson--out of the pawn shop for several hours a day. He does this by placing an add in the paper about a high-paying job for a man with red hair. Apparently, this job was created by a man with red hair who wanted men of his kind to get ahead in the world and involves his coming into an office for a few hours each day and copying the encyclopedia Brittanica. Jabez is fooled, and while he's at the office of the red-headed league, Clay succeeds in tunneling his way into the adjacent bank. He nearly steals the gold, but Holmes beats him to it.
“The Speckled Band” (1892)
In which the greedy Dr. Roylott--who used to serve as a physician in India and keeps a number of exotic animals in his Surrey estate--attempts to kill off his second step daughter, Helen Stoner, in the manner in which he killed his first, just before she married. His goal in doing so is to keep the inheritance that she is scheduled to inherit after her impending marriage. Roylott attempts to kill Helen by forcing her into her sister's room under the pretense that he is mending the outer wall of her bedroom and by then inserting a venomous swamp adder (Indian cobra) through a ventilator into her room. His plan backfires when he is bitten by the snake after Holmes startles the serpent back into Roylott's chambers just as the former is being led into Helen's sister's room. The mysterious "speckled band" Helen's sister saw just before her death turns out to be the swamp adder.
“Silver Blaze” (1892)
In which John Straker, the trainer of the prize-winning racing horse Silver Blaze, is killed after being kicked on the forehead by the horse after trying to nick its tendon and lame it so that he could influence the results of an upcoming horse race and make a small fortune--something he needs to support the lavish and expensive tastes of his mistress.
“The Final Problem” (1893)
There's not a mystery or whodunnit at the heart of this story; instead we have a longstanding rivalry coming to a climax, the rivalry between Holmes and his nemesis Dr. Moriarty. In the beginning, we discover that Moriarty has had his men try to kill Holmes three times (in a crash, by a thug, and by dropping a brick), but to no avail. Holmes escapes with Watson to the Swiss Alps, but Moriarty is on them like a hound. Holmes, concerned for Watson's safety, urges the latter to return to England, but Watson refuses to leave his best friend behind. Finally, Moriraty catches up and fights Holmes to death against the dramatic backdrop of Reichenbach Falls, while Watson is back at the village, responding to a fraudulent note claiming that a woman at the inn was ill and needed his medical help. Watson rushes toward the falls to help his friend when he realizes he's been tricked with the note, but it's too late; Holmes is (supposedly, until Doyle resuscitates him in "The Empty House") dead. Watson reflects that Holmes was one of the greatest men he ever knew.
"The Dancing Men" (1903)
This one owes a debt to Poe's "Gold Bug," which also has a substitution chipher at the heart of the story. In Doyle's story, Abe Slaney journeys to England and chases down the recently married daughter of the Chicago crime boss he works for, Elsie. Elsie flees Chicago because she doesn't want to be involved in the family's dubious criminal activities. She falls in love with Hilton Cubitt of Thorpe Manor in Norfolk, and the two marry, although Elsie makes Cubitt promise that he will never ask her about her past, although she is totally innocent. He agrees, and they enjoy a short period of blissful married life until a series of mysterious messages involving dancing men keeps appearing on Cubitt's manor--messages which terrify Elsie and perplex her husband, who turns to Holmes for help. Sadly, Cubitt is shot by Slaney when trying to save Elsie, who was on the verge of virtually being abducted by Slaney. Thanks to Holmes, Slaney is gradually caught, and, after recovering from her attempted suicide, Elsie recovers and inherits the manor.