Spiritualism, a religious movement that touted a belief in the ability of the living to communicate with the spirit world, enjoyed a period of popularity from the 1840-1920s. The bloodshed of the Civil War and WWI left a whole lot of people missing their loved ones, and wishing they could somehow breach the chasm between our world and whatever may come next. The movement embraced a generally paranormal worldview, touting everything from clairvoyance to spiritual healing.
Sir Arthur Conan Doyle, creator of Sherlock Holmes, was among the most passionate converts to the Spiritualist cause. The author wrote passionately about the power of séances, embarked on a world speaking tour to win converts to the cause, and even broke up his bromance with Harry Houdini when the magician spoke out against the faith. Doyle took his biggest pro-Spiritual stance in 1922, when he published The Coming of the Fairies. And no, it wasn’t a novel.