After three failed marriages, it looked like in 1996 she had met Mr. Right. Cook was a handsome, charming Hamptons architect who designed multimillion-dollar estates for New York's rich and famous. The couple wed when Brinkley was 42, and outwardly at least, they were a happy, glamorous celebrity couple who by all accounts really loved each other.
But eventually, Cook says, things changed.
"At some point I realized my needs hadn't been taken care of, and I took the cowardice way out and had an affair instead of approaching my wife and saying, 'You know what? I'm not happy.'"
Although he's not sure exactly when their marriage broke down, Cook says he was seeking attention and acknowledgement for his contributions to the family.With Cook' s advice, Brinkley bought and resold 18 properties reportedly increasing the family's worth five times over, to between $60 and 80 million.
He says he restored many of the 18 properties Brinkley purchased while with him, which increased the family's wealth five times over to a reported $60 million to $80 million.
"I wanted a little thank you every now and then for the amount of time I took to care for her and my family, for the wealth I was building," Cook said.
Cook says despite what he was feeling, he understands Brinkley's anger.
"Christie is mad at me. She's entitled to be mad at me. I'm an idiot. I made a mistake," Cook said.
Cook told Walters he met Bianchi when she was 17 years old and working at a toy store in Southampton, N.Y. She needed a better paying job and he needed an assistant.
"I needed this help done and if anyone's gonna do it," Cook said, "why not this cute, sparkling girl?"
Cook says he did not intend to have a relationship with her, but mutual attraction turned to flirting, which then turned into a consensual relationship.
"We weren't looking to build a life," said Cook. "It was about sex. It was something we both wanted."
Cook said he and Bianchi had sex nearly a dozen times, having trysts in his office and in various vacant homes that he and Brinkley owned. He said he strayed from his marriage because he was seeking a connection he wasn't getting at home.
"I just suddenly realized when I was getting attention from someone else, that this is something that is missing in my life," he said.
Cook says the affair had been over for months when, in 2006, he attended a speaking engagement with Brinkley where they were approached by Bianchi's stepfather, who demanded that Cook end the affair with his teenage daughter.
Brinkley was devastated and Cook says he knew at that moment that his marriage was over.
"I felt horrible," he said. "I felt horrible for what I'd just done to my family."
In that moment the 10-year marriage evaporated. Cook says he left with one suitcase.
"There was never a chance to heal our family," Cook told Walters. "What I had done was wrong. From the day she found out, I was dead to her."
After he told Brinkley the details of the affair, Cook also told her about his interactive involvement in online porn, going so far as to give her his passwords to the lurid Web sites where he watched pornography and participated with strangers in online sex acts.
"I told her everything," he said.
The media reported during the trial that Cook had a $3,000-a-month online porn habit, but Cook says this is untrue.