ABC News' Juju Chang and Gary Wynn report:
Jane Fonda has been famous her whole life.
The Hollywood legend from an acting family has won two Academy Awards, been criticized for her radical political views and led a fitness empire.
Even though Fonda has lived a public life, there is at least one thing that might surprise people about the former wife of billionaire media mogul Ted Turner.
In addition to her two biological children, Fonda has another daughter: Mary Williams.
Their complicated relationship began as a friendship, and Williams lays it all out in her new memoir, "The Lost Daughter."
Fonda and Williams sat down for an interview in Hollywood with ABC News' Juju Chang to discuss how it all began.
They met at a summer camp that Fonda ran with her then-husband, politician and activist Tom Hayden.
"When she showed up at camp … you could tell that she was a special person. And she came back for several years. And then she didn't come back …," Fonda said in the interview that aired today on "Good Morning America."
Williams grew up poor in Oakland, Calif. Her family belonged to the Black Panthers. Life in the tough neighborhood eventually took its toll, and Williams became the victim of a sexual assault when she was 14.
Fonda made her an offer.
"Her grades were failing. I mean … this is a hugely smart person, but she was failing. I said, 'If you bring your grades up … by the end of the year and your mother permits you, you come down and live with us in Santa Monica,'" Fonda, 75, said.
Williams remembers how things were back then.
"I literally felt like I was dying. I really did," she said. "And when I saw that opportunity, I ran. I ran for it."
Suddenly, Williams was taken from her inner-city neighborhood and found herself living in beautiful Santa Monica as the daughter of a screen icon. It was a shock for her, and there was more change on the way.
"I had no idea that, at the time, I was going to end up married to Ted Turner, and my black daughter was going to end up sitting at a table in a southern plantation, you know, being served by black people, the only black person at the table," Fonda said.
Williams was a quick study. She merged her old family's values with her new ones, and in her book she explained that the two worlds weren't so different.
"The Black Panthers, the Fondas, and the Turners, are as different as families can be," she said. "But they all had one crucial thing in common: They were not shy about acting on their political beliefs … For them, the highest form of patriotism was dissent, all in the spirit of trying to make the world a better place."
Williams had troubled shedding her troubled past and it threatened her relationship with Fonda.
"I was slowly realizing I was alienating myself from people. … And the fact that I did it to the person who I love the most in the whole wide world made me realize that I was really in crisis, you know, and something was really out of whack," she said.
When Chang pointed out that Williams had said she loved Fonda most in the world, Fonda replied: "Don't say it again, I'll start crying. Yeah. Isn't it beautiful?"
"Well, you are," Williams said to Fonda.
Williams threw herself into her work, and she focused on helping others. She taught English and worked for the United Nations in Morocco. She also worked in rural Tanzania, and helped relocate hundreds of Lost Boys in the Sudan, and conducted research in Antarctica.
Williams also hiked the Appalachian Trail and bicycled across the United States. Through all her activities, she was conquering her fears, but she said she was also running away from the anger she felt toward her biological mother.
Fonda, who accompanied Williams on her search for her birth mother, described it as "a wild experience.
"Three of us went to lunch … You know, me, white, privileged, movie star. And this woman who's had a really rough life, she didn't seem to be angry, she didn't seem to be resentful. She has a good sense of humor," she said of Williams' birth mother.
Chang asked Williams whether it would be an overstatement to say that Fonda saved her life.
"It is not an overstatement at all," she said. "I mean, she doesn't know how amazing she has been and what she has done."