The Case for Spirit Photography is Arthur Conan Doyle's nonfiction treatise defending the validity of spirit photographs – images that allegedly capture ghosts or spirit forms. In this illustrated work, Doyle investigates famous cases of spirit photography, including the controversial Cottingley Fairies photographs and portraits by mediumistic photographers like William Hope. He lays out evidence and firsthand accounts to argue that these eerie images, showing faint figures or ectoplasmic shapes, are genuine proof of spirit existence rather than fraud. Doyle addresses common skeptical explanations (double exposure, etc.) and counters them with technical analysis and testimonials. The book features reproductions of several spirit photographs, which Doyle guides the reader through, pointing out hazy faces or forms said to be deceased persons. Throughout, Doyle's tone is earnest and advocative; he believed that if the public examined the facts and patterns in these photos, they would realize an "epoch-making" truth was at hand. The Case for Spirit Photography serves as a snapshot of early 1920s spiritualist belief, with Doyle as a passionate attorney presenting what he sees as hard visual evidence from the other world.