Sherlock Holmes: A Drama in Four Acts is a stage play co-authored by Arthur Conan Doyle and actor William Gillette, bringing the famous detective to life on the late Victorian stage. In this original story (set in 1880s London), Sherlock Holmes faces off against criminal mastermind Professor Moriarty while juggling a delicate romance and protecting a young woman from peril. The play condenses several Holmes adventures into one suspenseful narrative, featuring iconic elements like the Baker Street sitting room, fiendish traps set by Moriarty, and Holmes's dramatic disguise and escape at a foggy moor. Gillette, who also portrayed Holmes on stage, infused the script with action, humor, and even the immortal line, "Oh, this is elementary, my dear Watson." The drama was wildly popular, solidifying Holmes's image (deerstalker, pipe, and all) in the public imagination. As a published script, it offers a unique, theatrical take on Holmes, full of derring-do, comedic asides by Dr. Watson, and the ultimate triumph of good over evil under the footlights.