(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."
"You could see the pressure of the pen. Obviously she was angry with herself," Chrissie said. "To have a glimpse into somebody's mind like that -- how difficult it was for her to figure out a phone number that she has phoned for so many years. It's scary."
We leafed through the pages of this small book as we talked to Chrissie. And though we had never met Doreen, it was painful for us to read these outbursts from a woman so trapped in her own mind. But this all came later. The first time Chrissie began to realize how bad things had gotten was in the winter of 2010, when she helped her mother go through all the paperwork that had been building up in the condo where Doreen lived alone.
It was all so out of character. Doreen was once frugal and practical to a fault, owning her own successful business and managing her family's finances at a time when few women did so. Now she seemed to have become an entirely different person. Doreen's children found buried within the piles of coupons, magazines, junk mail, and the occasional misplaced sock a bill from a department store credit card with a shockingly high balance. Concerned, Chrissie dug into the rest of her mother's finances. And when she turned to her mother's bank statements, she saw a disturbing number of payments to two names she didn't recognize: Destiny Research Center (while this name would remain a mystery to Chrissie, it would become very important to us) and Maria Duval. Every check was made for the same precise amount of $59 (in Canadian dollars).
"Who is this? What is this place? What are you getting for this money?" Chrissie asked her mother.
Suddenly, her mother's pleasant demeanor was gone. She turned defensive and secretive, and simply shrugged in response to Chrissie's questions and admonishments. "She was unable -- not unwilling, but unable -- to specify what she was getting in return for this amount of money," Chrissie remembers. "She finally showed me large round metal talismans encased in little velveteen pouches with symbols and some with motivational words or astrological signs on them."
It was soon evident to Chrissie that the cheap trinkets and the mysterious woman from the letters were an inescapable presence in her mother's life.
When Doreen was at her best, Chrissie convinced her that the letters were a terrible scam that was stealing her retirement savings.
This realization took a huge toll on Doreen. "She was shocked, dismayed, and ashamed when she realized her stupidity and the financial damage she'd caused herself," Chrissie said. "I gave Mum strict orders to throw away anything from Maria Duval or Destiny Research; she seemed to understand my frustration and anger (at this scam) and readily agreed."
Still, as her memory declined, Doreen returned to her secretive relationship with Maria, almost like a child hiding a secret stash of candy from her parents.
Even after Chrissie and her brothers took away Doreen's checkbooks and assumed legal responsibility for her finances, she would cobble together piles of cash and coins to make up the amount Maria was requesting from her.
From two years' worth of bank statements, Chrissie is certain that Doreen sent at least $2,400 to the psychic. Her total losses were likely much larger.
"These scammers seem to have targeted my mother as easy prey, probably from the very first check she sent to them," Chrissie told us. "Not only was my poor mother quickly losing her mind due to Alzheimer's disease, she was lonely, bored, (and) wanting to be wealthy and well. She didn't have the quality of mind anymore to realize how much money she was losing or how often she was sending money!"
Finally, knowing that the painful tug-of-war with her mother wasn't going to get her anywhere, Chrissie turned her anger and frustration to Maria. She reported the crime to the police, but they told her there was little they could do to help recover any of the money Doreen had given away. So she sent letter after letter to the address on the solicitations, tersely demanding a refund ("of any amount -- even just $59.00 to show good faith") and for Doreen's name to be stripped from the mailing list. Her efforts proved fruitless. So Chrissie's brother finally resorted to forwarding Doreen's mail to his own home, where he could sort through all the junk mail and scam letters, keeping only the bills and other important documents. At one point, he received thirty-six scam letters in a single day, all addressed to Doreen.
As Chrissie's brother handled all the mail, Chrissie turned into an armchair detective, scouring the internet in an attempt to uncover which heartless criminals had gotten their hands on her mother's hard-earned money.
"It was painful. Then it was frustrating. Then I just grew angry," Chrissie said. "I'm not an angry person by any means. It takes a lot to get me mad but, boy oh boy, to find out how long they had taken advantage of this woman who believed that she was getting something for her money."
Chrissie spent months trying to get to the bottom of the fraud.
When her mother passed away a few years later, roughly a year before we began our own hunt for answers, Chrissie still had no idea who was behind the Maria Duval letters.
• • •
Maria's victims are all over the world, but they have one thing in common: desperation. We found stories from her victims everywhere we looked -- online, in old newspaper clippings, and in the many government documents detailing the scam.
Many of the victims reminded us of Doreen: Suffering from illnesses that were chipping away at their brains. Lonely after spouses and friends had passed away. Living on a fixed income and worried about everyday bills or the money they were going to be able to leave behind.
"He is so desperate for money that he pins all his hopes on this," one person wrote online about their 96-year-old father-in-law, who refused to believe that the letters were a scam and even tried to send a cash payment after his family closed his bank account.
In a letter to Maria that was found by US authorities, another victim wrote that she was in such serious financial straits that she was struggling to afford new glasses or a dentist appointment. She apologized to Maria for not writing more often, telling her that she was "in distress" with back problems. "I am getting more broke every day. I can't send what I don't have."
We wanted to understand why these people were the perfect targets. So we called Dr. Peter Lichtenberg, a clinical psychologist and the director of Wayne State University's Institute of Gerontology, who has studied the financial exploitation of the elderly and the underlying psychology of scams for years.
"It's a combination of loneliness, depression, and a real sense of invisibility," he told us when we asked him what made people fall for a scam like the Maria Duval letters. This isolation and psychological vulnerability creates the perfect setting for a scammer to enter people's lives. As they are feeling invisible to society and even to their own families, suddenly someone out there -- in this case, a woman who looks so trustworthy and kind from her photo alone -- has chosen them and is giving them the attention they have been missing.
For those who feel like they have lost their sense of self, this scam makes them feel important. The promises of financial windfalls also tap into the overwhelming desire at this stage in people's lives to be able to create a legacy for future generations.
To make matters worse, many people suffering from dementia are more likely to become secretive or suspicious of their own family members, especially if those individuals are attempting to pry into their finances or personal lives. This makes someone like Maria, whose letters profess love for who they are and an understanding of everything they're going through, that much more attractive. And it makes it even harder for families to break through.
The Maria Duval scam reminds Dr. Lichtenberg of a cult in the way that it creates a special relationship with its victims that is entirely resistant to logic. "The key is almost cult indoctrination. ... They're so far in, you have to cut the contact off in order for them to come back to reality, he said. "It's the leader, the belief in this person, in this woman and her magical gifts and her specialness."
Hearing this, we thought about how family members told us about letters warning victims to keep their relationship with Maria a secret, one that outsiders simply wouldn't understand. Dr. Lichtenberg said that even mild symptoms of aging can affect someone's ability to reason -- a person doesn't need to have severe cognitive impairment.
Deteriorating memories can also play a role in an individual's susceptibility to such a scam, as many victims are unable to estimate just how much money they've been sending. Some of Maria's victims weren't elderly or cognitively impaired at all. Rather, they were simply lonely. And others just seemed more easily persuadable, trusting to a fault.
"I have sent this woman lots of my money where I could not pay my bills," a mother of five wrote in an online consumer complaint forum in 2014, saying that she was living on a fixed income and thought that sending money to Maria would help bring about a better life for her children. "Yes I feel like a fool, but when you receive (these) letters over and over you feel like a failure if you did not send it in to get a better life for your children." In another online complaint, a woman from Michigan recounted how Maria's letters had come to her in some of her darkest days -- soon after she separated from her husband, lost her job, and said a hard goodbye to her son, who had joined the military. "This scam crushed the last bit of hope I had in any kindness or miracle that could be, and pushed me over the edge," she wrote. "Congrats! You got another weak one."
It wasn't surprising for Dr. Lichtenberg to hear that it wasn't just the elderly who were being duped by this scam. The same desperation can attack anyone's judgment, he told us, whether someone is dealing with a death in the family, job loss, financial misfortune, or depression. "The human condition is not all that different throughout life," he said. "People get the feeling of invisibility and think, 'This is not what life should be, this is not what I expected life to be.'"
In some cases, Maria's letters have taken a more sinister tone, suggesting that misfortune awaited those who ignored her. In 1997, one woman told the Scottish Sunday Mail newspaper that she was terrified of what would happen if she didn't send money. "When I wrote to say I didn't have that kind of cash, the letters got even more frightening," she said at the time. "I was so scared I couldn't eat or sleep, worrying whether I'd be hit by more bad luck."
Dr. Lichtenberg said that scare tactics like this can be incredibly effective, and in many cases they are employed as a last resort to get a victim's money. "It's all sweet and nice as long as the cash is coming, and if that stops it can get very dark," he told us. "The path of least resistance is to just send more money."
Listening to Dr. Lichtenberg talk, we realized that this scam truly used every tool in the book. Other popular schemes seemed to rely on one main emotion. Schemes promising lottery wins rely on hope. Romance scams, in which fraudsters develop fake relationship with victims, rely on loneliness. And so-called grandparent scams that convince family members to wire money to a loved one they claim is in crisis rely on fear. But Maria's letters use a combination of all these emotions.
This is what made the scam so powerful. The letters appealed to the most base emotions of fear, loneliness, and hope -- making it nearly impossible for victims to resist.