"He was constantly on the Internet, reading every article, reading every blog, reading all the nasty comments that come with all of those articles on the Internet," said Mack. "He physically changed. He wasn't doing the things he liked to do anymore. He grew in a beard to try to disguise himself, he was physically hunched over. "
In June of 2009, Bernie Madoff pleaded guilty and was sentenced to 150 years in a minimum security federal prison. Determined to make Madoff suffer even more for what he had done to his son, Mack wrote a letter to him describing the life he would forever be missing with his two grandchildren.
Instead of showing remorse, Madoff wrote back bragging about his new life in prison, telling Stephanie that he was treated as a celebrity.
While Bernie Madoff was apparently basking in his famous status, his son continued to be consumed by the shadow of Bernie's shame. In her book, Mack reveals that in October of 2009 her husband failed in a previously unreported attempt to take his own life. Mark had walked out of the couple's Soho apartment, checked himself into a hotel and swallowed 60 sleeping and anti-anxiety pills. However, the suicide attempt failed and Mark returned to his apartment, groggy and incoherent. Mack said a suicide note was later found in the hotel room, that read: "Bernie, now you know how you have destroyed the lives of your sons by your life of deceit. F--- you."
Mark Madoff was admitted to a psychiatric ward, where he slowly recovered. By summer of 2010, Mack said she was confident that her husband had turned a corner, and that he was focused on their two children and excited about new opportunities, such as a real estate newsletter that he had created.
"He would come home from work every day happy," said Mack. "He wasn't being brought down by all this crap that had been thrown his way."
But in December of 2010, while Stephanie, her mother and her daughter Audrey were vacationing in Disneyworld, Mark again went into a downward spiral. He learned that his 4-year-old daughter was being sued for $11,000 gifted to her by Bernie and Ruth and there was a new article in the Wall Street Journal hinting that he could still face criminal charges.
On the morning of Dec. 11 -- two years to the day after his father's arrest -- Stephanie woke to an email from her husband. The subject line of the email was "HELP" while the body of the message said, "Please send someone to take care of Nick," the couple's 22-month-old son. The next email simply read: "I love you." Panicked, Stephanie immediately contacted her stepfather in New York, who found Mark Madoff's dead body hanging from a ceiling beam.
"I think he thought that we would be better off without him," a tearful Mack said. "Which makes me so sad, because that's not the case at all."
Even in death, the whispers and suspicions continue to follow Mark Madoff, with some press accounts suggesting that he killed himself because he was part of his father's crimes. Mack told ABC News that nothing could be further from the truth.
"My husband's death was only proof of his pain," she said. "My husband was in terrible, terrible pain. He was so deeply hurt by it all, that he just, he, he just couldn't move past it."
With Mark's blessing, Stephanie changed her last name to Mack to spare her family the stigma of that now reviled name. Today, her children are healthy and happy and Mack says she intends to keep them that way.
"I will never let it define my two children for the rest of our lives," she said. "The rest of my life is going to be a happy one, and not filled with deceit, and lies, and betrayal, and sorrow and I hold onto that hope."
Watch the full story on "20/20" Friday at 10 p.m. ET.