If modern movie and TV versions of the world’s most famous detective have taught us anything, it’s that the popularity of Sherlock Holmes is forever ingrained in our collective pop-culture memory. Even Star Trek told tales of Holmes and Watson through the lens of the 24th century. But the man who brought Holmes to the world—Sir Arthur Conan Doyle—was a bit of a detective in his own right. And in the early twentieth century, he became involved in a supernatural investigation of his own that would give Sherlock a run for his money.