After extensive travelling abroad, Doyle returned to the States to continue his lecture tour and, in Denver, he met Houdini. They had long discussions about Spiritualism and some recent psychic investigations. Doyle had witnessed a demonstration by the Zancig, a couple of vaudeville mind-readers, and was convinced they were real telepaths. Houdini, however, knew them personally; they were acknowledged magicians and members of the Society of American Magicians, but nothing of this moved Doyle. "Sir Arthur said that he was capable of detecting trickery," wrote Houdini in his notes, "and we had a discussion in which I said that I did not think he could. He looked amazed at me, and I said, 'Why, every once in a while I see something I cannot account for'". While staying in Denver, the local newspaper interviewed Doyle; the reporter told him that Houdini was offering five thousand dollars for any medium's feat he could not duplicate, and Doyle said that he would give the same amount of money if Houdini could "show me my mother". Immediately, Doyle apologized to Houdini, saying he had been misquoted.

Spiritualism brought Houdini and Conan Doyle together in 1920, but it was hardly the only thing they had in common. Both men were famous around the globe, and while their career paths were quite different they shared an energy and a virility that few could match. Houdini’s athletic feats were obviously central to his act, and although more famous as a writer, Arthur Conan Doyle was an avid sportsman and adventurer, a large man who struck many as the very embodiment of English manhood. But for all their similarities, the men had divergent approaches to Spiritualism.

After a séance in which he believed he had been contacted by his son Kingsley, who had died in the War, Conan Doyle became a leader of the movement, defending it in lectures around the world. Even the embarrassing Cottingley fairy hoax, in which he had championed faked photographs of wood fairies and goblins that were later revealed as fakes, did not deter him. "The Elusive American," Houdini, on the other hand, thought he knew trickery when he saw it, and set out to punish those taking advantage of a vulnerable public. That their friendship lasted for several years is largely due to the fact that Houdini, always seeking intellectual respectabilty, deliberately hid his real feelings about Spiritualism from Doyle.

Soon after their correspondence had turned into a friendship, introductions from Conan Doyle gave Houdini entrée to dozens of mediums during an extended tour of Great Britain. Unknown to Doyle, however, Houdini was far from converting: "The more I investigate the subject," he wrote, "the less I can make myself believe." Inevitably, despite a growing personal friendship, the two great men moved toward a confrontation.

Their falling out began when Houdini joined the Doyles for an intimate séance, in which Lady Doyle proposed to contact Houdini’s beloved mother. Although a skeptic, Houdini did believe in an afterlife, and as biographer Kenneth Silverman wrote, "closed his eyes and tried to rid his mind of all but religious thoughts." But by the time Lady Doyle had filled fifteen sheets with automatic-writing she claimed had come from Cecelia Weiss, Houdini had only become further convinced that he was witnessing a fraud. Although he left without disclosing it -- "I did not have the nerve to tell him," -- Houdini knew that he had not heard from his mother. A rabbi’s wife, she never would have begun with a sign of the cross; although she had barely uttered a word in English while alive, suddenly she was fluent, saying things like "I am almost overwhelmed by this joy." It simply did not sound like his dear mother, and Houdini resented it.

Although they both tried to prevent it, Houdini and Conan Doyle were arguing privately over medium cases within months; by the spring of 1923, they were exchanging sharp letters in the "New York Times." After a public feud when their tours crossed in Denver, the friendship seemed beyond repair. While praising him as "the bravest man in our generation," Conan Doyle condemned Houdini for being biased and publicity hungry. Houdini wrote that "There is nothing that Sir Arthur will believe that surprises me." It had been one of the oddest pairings of the century. Their meeting at the Ogden Theater was to be the end of their friendship.