«The Man with the Twisted Lip» by Arthur Conan Doyle

"The Man with the Twisted Lip", one of the 56 short Sherlock Holmes stories written by Sir Arthur Conan Doyle, is the sixth of the twelve stories in The Adventures of Sherlock Holmes. The story was first published in the Strand Magazine in December 1891. Doyle ranked "The Man with the Twisted Lip'' sixteenth in a list of his nineteen favourite Sherlock Holmes stories.
Late at night, Kate Whitney, a friend of Dr. Watson's wife, calls on them. Her husband, Isa, has been absent for several days. Frantic with worry, she begs Dr. Watson to fetch him home from the opium den where he goes. Watson does this; but he also finds his friend Sherlock Holmes in the den, disguised as an old man, seeking for clues among the habitués of the place.
The case involves Mr. Neville St. Clair, a prosperous, respectable, punctual man, who is missing. His family's home is in the country, but he visits London every day on business. One day when Mr. St. Clair was in London, Mrs. St. Clair also went to London separately. She happened to pass down Upper Swandam Lane, a "vile alley" near the London docks, where the opium den is. Glancing up, she saw her husband at a second-floor window of the opium den. He vanished from the window immediately, and Mrs. St. Clair was sure that there was something wrong.
Famous works of the author Arthur Conan Doyle's: "A Study in Scarlet", "Silver Blaze", "The Hound of the Baskervilles", "The Yellow Face", "A Scandal in Bohemia", "The Red-Headed League", A Case of Identity", "The Boscombe Valley Mystery", "The Five Orange Pips", "The Man with the Twisted Lip", "The Blue Carbuncle", "The Speckled Band", "The Engineer's Thumb", "The Noble Bachelor", "The Beryl Coronet", "The Copper Beeches" and many more.