Mary Jo Eustace ...Dean Mcdermott's ex wife...SPEAKS OUT.

It was one of the more famous breakups of the time, even though the central parties involved weren't well known: Mary Jo Eustace and her actor husband, Dean McDermott. But then, he left her for Tori Spelling.

"My birthday weekend last year, I came home, and somebody called me and said there was going to be something in [New York Post gossip column] Page Six, and I didn't even know what Page Six was," Eustace, 45, tells PEOPLE. "So it just kind of exploded. ... I was offered several publishing deals to do a book, and I turned them down."

When The Other Woman Is Tori Spelling?

When Dean called me from the set [of his TV movie], he told me how great he was getting along with his costar Tori Spelling. She was fun, caring and much hotter in real life. I assumed this was good. Before he left, jokes flew at the prospect of working with the daughter of a Hollywood mogul. I suggested he befriend her. "Who knows?" I laughed. It might be good for his career.

Now here he is, back. We're on vacation and I'm wearing my bikini with saggy faded bottoms. I know something is wrong. "Have you met someone?" I ask. He nods yes. "Is it Tori Spelling?" He nods. "We're soulmates," he says. "She loves me unconditionally." "What conditions?" I scream. "You've only known each other three weeks."

I look down at my baby daughter. "We just adopted a baby." The phrase single mother pops up in my brain. I start to feel weightless as I cross the divide between together and alone. "I'm not leaving the kids," he says. "I'm leaving you." I begin to sob. I actually begin to worry that maybe it's all because I look fat. Maybe he was undecided, and this dreadful bikini sealed the deal.

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