Geoff Manaugh at Cabinet Magazine:
The books and manuscripts were disappearing from a room no one seemed to be entering. Its doors were almost never opened, the room itself closed to public view. There was no believable explanation for where the materials might be going, so the least believable reasoning soon took hold. It was the work of the devil, the residents said. A poltergeist. A symbolic act of God meant to communicate something, if only they could interpret the signs.
This was, after all, a monastery—indeed, one of the world’s most picturesque, Mont Sainte-Odile, perched high in the mountains of France, nearly on the border with Germany—and its library was vanishing into thin air. A manuscript here, a bound volume there; five, six, a dozen, all quickly adding up to nearly a thousand key pieces of church scholarship missing from the shelves and tables.
When the police were finally notified, they chose not to perform an exorcism. Being a secular institution, they instead installed a hidden surveillance camera, and, in May 2002, the truth came to light. It was not a ghost at all, but an engineering teacher from Strasbourg. He had been entering the room through a long-forgotten secret passage, access to which was hidden inside one of the bookcases. Unseen—indeed entirely unsuspected—he was able to remove the library’s priceless collection piece by piece, emerging from the walls to take entire shelves of books at a time.
more here.