Arthur Conan Doyle’s The Great Keinplatz Experiment and Other Tales of Twilight and the Unseen is a collection of short stories written in the early 20th century, focusing on themes of the supernatural, psychology, and the unseen forces that influence human life. This anthology delves into encounters with ghosts, inexplicable phenomena, and psychological mysteries, often featuring characters such as doctors, scientists, and individuals confronting the unknown.
The opening story introduces Dr. Hardacre, who becomes the heir to his wealthy uncle, Sir Dominick Holden, a once-renowned Indian surgeon. Sir Dominick has been tormented for years by a haunting apparition: the ghost of a one-handed Indian man who demands the return of his severed hand. Over dinner, Sir Dominick reveals how this supernatural encounter has reduced him to a nervous wreck. Intrigued, Dr. Hardacre decides to stay the night at the estate to investigate the phenomenon for himself.
This story sets the tone for the collection, exploring the intersection of science and the supernatural, as well as the psychological impact of fear and the unknown.

I. THE BROWN HAND
II. THE USHER OF LEA HOUSE SCHOOL
III. B. 24.
IV. THE GREAT KEINPLATZ EXPERIMENT
V. CYPRIAN OVERBECK WELLS A LITERARY MOSAIC
VI. PLAYING WITH FIRE
VII. THE RING OF THOTH
VIII. THE LOS AMIGOS FIASCO
IX. HOW IT HAPPENED
X. LOT NO. 249
XI. "DE PROFUNDIS"
XII. THE LIFT