From 1918 until his death in 1930, Arthur wrote eleven books proselytizing spiritualism, plus numerous pamphlets, articles, and letters to make his case. To spread the word, he lectured throughout Britain, the United States, Canada, Australia, New Zealand, and Africa. He opened his own psychic bookstore.

Strangely, he established a fractious friendship with Houdini, the great magician who spent so much time debunking claims of the supernatural, explaining and demonstrating how so-called psychic phenomena were nothing more than crude magic tricks. Though Houdini refused to reveal how he accomplished his own tricks, he never denied that they were accomplished by natural means.

Arthur, being unable to conceive of how Houdini accomplished his many escapes, simply concluded that Houdini was one of the great mediums of all times who accomplished his feats by supernatural means. In fact, Arthur deemed his insight to be a great discovery, one of which the world should be made aware. To Houdini’s biographer, Harold Kellock, Arthur wrote, “I think, however, that you may take the words ‘An Unsolved Mystery’ off your cover. It is I who have solved the mystery of Houdini and I have no more doubt that he used psychic powers than I have that I am dictating this letter.”

Arthur was fooled not only by young women with unusual appendages, by girls with scissors and a camera, and by a dog that wouldn’t stop yipping, he was fooled most thoroughly by himself. The creator of Sherlock Holmes must have been someone less silly and gullible than Arthur Conan Doyle.