The True Story Behind Netflix’s Devastating Scammer Documentary Con Mum
The Netflix documentary Con Mum brings to light an unbelievable story that seems straight out of a Hollywood movie script: a son reconnecting with his biological mother after more than 40 years apart, only to discover she wasn’t exactly the maternal figure he had expected. At the center of this story are Graham Hornigold, a renowned British pastry chef, and a woman who goes solely by the name Dionne, who claimed to be his mother and would turn his life upside down in the months that followed their reunion.
[time-brightcove not-tgx=”true”]Here’s the story behind Hornigold, Dionne, and the con that cost so much more than just money.
Read more: Here’s What’s New on Netflix in March 2025
The email that changed everything
In 2020, Hornigold’s life was in a great place. He had solidified his career in high-end gastronomy and was about to become a father. But an unexpected email stopped him in his tracks. A woman named Dionne reached out claiming to be his biological mother, including precise details about his birth in order to make her case. At first, he thought it was a joke. But what if it were true?
Hornigold’s childhood hadn’t been easy. Raised by a father he describes as strict and abusive, he never really knew what happened to his mother. Her name was on his birth certificate, but any attempts to find her had been fruitless. Until that email.
“Hi Graham, I’m not sure if this is going to reach you as I’ve been searching for a way to contact you and found this email,” she wrote. “My name’s Dionne, formerly known as Theresa … Graham was born in Germany before being taken away from me to England,” she wrote.
It was enough to convince him to give her a chance.
Read more: Why We Can’t Look Away From Scammer Stories
The emotional reunion
Graham and Dionne met in person shortly after the email exchange. Her charisma helped her to quickly win over her long-lost son. The moment of their first meeting was captured on video, immortalizing what seemed to be an emotional reunion. But soon, strange signs began to appear.
Dionne told Graham that she had a terminal illness and only a few months to live. She also claimed to be extremely wealthy, heir to a fortune tied to Southeast Asian royalty. At first, none of this mattered to him. All he wanted was to make up for lost time with his mother.
“If I die soon… you are a multi-millionaire. That’s all I can tell you. I’ll put everything in your name,” Dionne told Hornigold in a phone conversation, according to the documentary.
The luxury and the promises
Dionne spared no expense: she stayed in the finest hotels, dined at expensive restaurants, and made grand promises about the money Hornigold would inherit. She even bought cars for him and his partner, Heather Kaniuk. But there was one not so minor detail: all these expenses were actually coming from Hornigold’s own pocket. Dionne funded much of her lifestyle through money borrowed from, and never repaid to, Hornigold. Though she gifted him a car, she left him with the bulk of the payments.
Slowly, his life began to revolve around trips to meet with lawyers that never led to anything concrete about arranging for the alleged inheritance. Dionne always had an excuse for the delays. Meanwhile, Hornigold paid the bills, believing everything would be resolved soon.
Read more: 33 True Crime Documentaries That Shaped the Genre
The fraud begins to unravel
It was Kaniuk who first noticed something was wrong. The expenses were piling up, and Dionne’s promises were never being fulfilled. She also began to pick up on manipulative behavior, as Dionne attempted to drive a wedge between the woman and her newborn son.
The scam was fully exposed when Juan, a friend of Hornigold’s, decided to confront him—Dionne had borrowed money from Juan with the promise to repay it. After investigating, Kaniuk and Juan discovered that Dionne had deceived other people before them. But the most shocking revelation came when Graham found a bottle of red dye among his mother’s belongings. The blood she claimed to be losing due to her terminal illness was nothing but a trick.
The fall of Dionne
After realizing the truth, Hornigold cut ties with Dionne. The damage, however, had already been done: he had accumulated a debt of around £300,000 ($387,228). The woman he had so desperately wanted to find was in fact his biological mother. But her motivation for reuniting with him wasn’t to make up for lost time, he explains, but rather to run her schemes on him as a seasoned con artist.
Con Mum reconstructs this absurd and tragic story, laying out how Dionne managed to manipulate not only Hornigold but also many other victims over 40 years. More than just a financial scam, the case highlights the emotional impact of a deep desire for belonging—and how vulnerable that can make a person.
The consequences
More than a year after the last time he saw his mother, Graham received an unexpected call from Dionne. In the conversation, she said she loved him and apologized. However, for him, it was already too late.
Dionne—who has gone by many names over the years, including Dionne Marie Hannah and Theresa Haton Mahmud—chose not to give her side of the story for the documentary, nor has she discussed it publicly. She declined to speak with Netflix and, to this day, has never been criminally charged regarding the allegations made in the film. Though Kaniuk and Hornigold went to the police, they were told that Dionne’s relationship to them would disqualify her activities as fraud.
The impact of Dionne’s scam didn’t only affect Graham financially. The tension and stress caused by the situation also affected his relationship with Kaniuk. After all of this, the two ended up separating, and their son continued to live with Kaniuk.
In the end, Graham lost money, time, the stability of the family he had created, and the illusion of an ideal mother that might have remained intact had she never entered his life at all.