'Easy prey': How a massive psychic fraud gained its power

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(CNN)CNN journalists Blake Ellis and Melanie Hicken have spent years investigating one of the largest consumer frauds in history -- a case that has stumped global investigators for decades. The scheme, which duped victims out of millions of dollars with letters claiming to be from a famous French psychic named Maria Duval, is the subject of the reporters' new true crime book, "A Deal with the Devil." The following excerpt has been edited for brevity.

Chrissie will never be sure when exactly her mother got her first letter from Maria Duval or how she became a target.
What she does know is that in the months leading up to her mother's eightieth birthday, before Chrissie or even Doreen realized that Alzheimer's disease was slowly and silently infiltrating her once rational mind, Doreen had handwritten at least forty different checks in response to Maria's letters, which Doreen believed were ending up with the psychic.
Chrissie suspects that her mother's obsession with these letters had far more to do with gambling on a cure for her failing mind than with winning a financial jackpot. In fact, Chrissie would later find evidence of an internal battle that Doreen hid from her children for years. She'd kept a Reader's Digest book full of brain games promising to keep her mind sharp. Not a single page was completed. And in her small personal address book was a page where she incorrectly wrote her son's phone number over and over again. On other pages, she furiously wrote her son's name repeatedly, sometimes followed by the words, "I kneed (sic) new shoes," and "Help me."