Harry Houdini is famous today as an escape artist, but his real passion in the 1920s was ghost busting. Or, rather, busting phony psychics who claimed to communicate with the dead. Spiritualism was extremely popular after the horrors of World War I, but Houdini, who had worked as a mentalist in his early years, was on to the tricks of the trade. He also resented the blatant frauds and blundering amateurs who tried to put him in contact with his beloved, deceased mother.
He recruited a squad to help him, including a female private eye, Rose Mackenberg. She was equally disgusted by those who preyed on the grief of others, and had a trunk full of disguises to sneak into suspect seances. A profile in Quartz detailed her detective skills:
Mackenberg quickly became Houdini's most prolific ghostbuster, often posing as a bereaved wife or mother. Her immensely detailed, mercilessly pragmatic reports earned her a number of enemies in the charlatan-spiritualist and ghost-racketeer community—forcing her to become a master of disguise. She might age herself with makeup or don a fake hearing aid to give the impression of impairment.
Houdini took his crusade all the way to a Congressional hearing, hoping to criminalize the practice. As reported in the Smithsonian, Rose was warned by a medium that they were fighting a losing battle.
At a May 1926 hearing, Rose Mackenberg, a woman Houdini had employed to investigate and document the practices of local mediums, detailed an undercover visit to Spiritualist leader Jane B. Coates, testifying that the medium told her during a consultation that Houdini's campaign was pointless. "Why try to fight Spiritualism when most of the senators are interested in the subject?" Coates asked. "… I know for a fact that there have been spiritual séances held at the White House with President Coolidge and his family."
That was one prediction the medium got right. Shut down by Congress, Houdini died soon after. But Rose claimed to have exposed hundreds of fakes before she too went to the great beyond.