The Case-Book of Sherlock Holmes is the final collection of Sherlock Holmes stories by Arthur Conan Doyle, containing twelve mysteries published between 1921 and 1927. In these later adventures, Sherlock Holmes faces some of his strangest and most unsettling cases, at times pushing the boundaries of the detective genre into darker or more fantastical terrain. Among the highlights: "The Adventure of the Sussex Vampire," in which Holmes investigates a family fear that a vampiric curse afflicts their household (only to find a very human explanation); "The Adventure of the Creeping Man," involving an elderly professor behaving like a ape after taking a mysterious serum; and "The Problem of Thor Bridge," a classic locked-room murder mystery with a brilliant solution. Readers also encounter "The Adventure of the Mazarin Stone," notable for being told in third person and staged almost like a one-act play (Holmes uses a wax dummy to outwit thieves) – it was adapted from Doyle's play The Crown Diamond. Throughout The Case-Book, Holmes is slightly older and occasionally more fallible, and Dr. Watson's narratives are tinged with an autumnal mood, as if aware these are their last published chronicles. Notably, two stories ("Mazarin Stone" and "His Last Bow") are not narrated by Watson, offering a rare outside perspective on Holmes. Doyle experiments with horror and exotic themes more than in earlier collections, leading to tales with intriguingly macabre touches such as "The Adventure of the Illustrious Client" (a battle against a sadistic nobleman) and "The Adventure of the Lion's Mane" (Holmes solo by the seaside solving a lethal jellyfish mystery). While some critics at the time found these later stories uneven, they remain rich in atmosphere and ingenuity. The Case-Book of Sherlock Holmes provides a bittersweet farewell to the great detective, showcasing his undimmed skill while venturing into new, sometimes eerie, territory – a fitting capstone to the Holmes canon that leaves readers with a final glimpse of Baker Street brilliance.