A year after the birth of their third child, Emily, in 1991, they separated, sharing joint custody of the children. Asked about McEnroe's assertion in You Cannot Be Serious that she was the first to call it quits, O'Neal counters, "He kicked me out of the house. He pushed me down the stairs. He almost broke my arm, almost broke my nose and called me every name in the book and blamed me for losing matches." Following their split, "I just didn't have a vision of how ugly it would become. It became a war."

At the end of 1994, O'Neal says, she hooked up with a young poet who introduced her to heroin. She started off sniffing, graduating to speedballs and, finally, needles. "It's not something I'm proud of at all," she says now. "I did it in my bedroom. Emily had to wait outside the door. Then one day she opened the door and saw. I realized it immediately and at that moment I told her that Mommy had a problem. That's easily the worst thing ever in my life." Today, she says, she tells her daughter, "If you need to be angry with me, be angry with me. Don't hold it in."

During O'Neal's heroin addiction, McEnroe got primary custody of the children while O'Neal went in and out of rehab. She says she cleaned up in 1998 with the help of therapy and Alcoholics Anonymous. Granted supervised visits with her children, she underwent twice-weekly urine tests until last summer, when, fed up, she stopped. "I'd spent about $20,000 on testing. I'd done it for four years. It was very demeaning. And it meant John still had some control over me," she explains. Tired of the legal wrangling, O'Neal says, she threw in the towel, giving McEnroe full custody of their children.

For a while O'Neal found a degree of happiness with Miramax executive Steve Hutensky, 37, whom she met at a wedding in 1998. After dating for almost two years, the pair became engaged on a carriage ride through Central Park in January 2000. But the wedding plans were short-lived. After Ryan was diagnosed with leukemia, O'Neal broke off the engagement and moved west to be near her dad. "I was a runaway bride," she says. "Steve's a great guy. I'm sure he's extremely pissed off. But I'm still fighting this first marriage." The breakup, coupled with her father's diagnosis, "sent me into a terrible spin," she says. She ended three years of sobriety by turning to cocaine.

It's a long path back, but O'Neal insists she has taken the first steps. "I think it would be terribly sad if I killed myself with my addiction," she says. "How sad would I be if I couldn't overcome my legacy? I tell myself that I have to channel it into art, work, loving my kids, living a good life. There are people who will love me if Ilet them."

Twice a month she visits New York City, where her three-bedroom apartment is just eight blocks from the Central Park West home McEnroe shares with their children, his second wife, rock singer Patty Smyth, 45, her daughter and their two kids. She sees Kevin, Sean and Emily only when McEnroe will allow -- which, in their current state of bitterness, she says, translates to seldom, if at all. Instead, they communicate by cell phone -- "I leave long messages, and they say, 'Geez, Mom, you're wasting my battery!' " -- and O'Neal spends much of her time at her home in West Hollywood. There, with her dog Lena, a Scottie, and cats Wallet, Zoey and Percy, she has settled into a quiet routine of weekly yoga, daily meditation and twice-daily AA meetings. She is also hoping to revive her acting career with a role in The Scoundrel's Wife, an indie film that is looking for a distributor. Meanwhile, despite her dad's reluctance to have a heart-to-heart, O'Neal is focused on making peace. "He's all I have," she says. "We may not have a great relationship, but he loves me to pieces, and I love him. And you know what? I forgive him."

-- MICHELLE TAUBER
-- TODD GOLD and LORENZO BENET in Los Angeles and KC BAKER in New York City

Photo Gallery: Tatum Through the Years