When I first came, I had what on the surface something that seemed to be like the perfect life, or a pretty good life. Reporter: Allison Mack didn't need coaching to sound convincing on this nxivm testimonial, after a decade-long run as Superman's best friend, Chloe Sullivan, on TV's "Smallville," she's a pro. Allison playing Chloe was essentially Superman's best friend. She loved him, desperately, but was never going to get him. Well that explains the walking magnet theory. I think the doctors flag it. There are some very clear parallels that you could perhaps draw between Chloe's relationship with Clark Kent and Allison's relationship with Keith raniere. Allison Mack was playing a young woman who is desperately devoted to a very charismatic, very powerful man. Yes, I know Allison Mack very well. Reporter: Sarah Edmondson says when Mack came to a weekend event in 2008, she quickly became a favorite of management. Why was she desirable? I believe she was another bright light. And she had a huge following. Lots of fans. And I think they thought this would be another big fish to catch. Reporter: Plenty of fellow actors have at least dabbled in nxivm. Aren't you tired of waiting? Reporter: There was Mack's co-star on "Smallville," Kristen kreuk. Her boyfriend, actor mark Hildreth. And "Hawaii five-0"'s grace park appeared in this video with Keith reniere. This incredible warmth, this incredible type of love. Reporter: Of these, Mack is the only one confirmed to have stayed with nxivm long-term. That kind of leads me to my next question, which has to do with authenticity. Reporter: She became so close to vanguard, she appeared in this video conversation with him. So one would say authenticity is being as you are. Reporter: His words literally moved her to tears. I don't know why. It makes me want to cry. It's beautiful. Why do you think that's -- So emotional for me? Yes. I don't know. I think because it seems like it's something I feel like I want it. Authenticity. That she fawns over him, and deifies him, and looks at him like he's the answer to all of life's problems. It makes me want to barf, to be honest. Reporter: In 2016, about the time prosecutors now say the secret sorority was forming within nxivm, Mack began tweeting at former "Harry potter" star and outspoken women's advocate, Emma Watson. Allison repeatedly tweeted at her that she loved what Emma stands for, that also she is a member of a human rights group, a women's movement group, that she thinks Emma would be very interested in. And to just let her know if she's free to chat. Reporter: Mack tried three times to get Watson's attention on Twitter, apparently with no luck. Another lesser-known actress was more receptive however to the lure of nxivm. Hey, welcome to teen life. Im India oxenberg. Reporter: India oxenberg joined nxivm and then the secret sorority. She may even have those initials branded on her body. Oxenberg's mother is a better known actress. Catherine oxenberg is best known for her role in the '80s hit drama "Dynasty." My name is Amanda, Amanda Bedford. Reporter: Later, she appeared with a very young India in this movie. Where is he? I locked him in the closet. Reporter: And a reality show called "I married a princess." But what she says is the reality of nxivm is something she now wishes she never shared with India. Once I found out about the sex, the branding, the slaves, I went nuts. Reporter: Oxenberg hasn't seen her daughter in months and is both gripped with fear and wracked with guilt. Because she herself brought India into nxivm. They went to an introductory session together in 2011. I just couldn't wait to get out of there and I said to India, "What do you think?" And she said, "This is for me." And I was in shock. Reporter: How old was she at that time? 19. Reporter: So pretty. Pretty young, pretty impressionable. Reporter: She says trouble started when India, seen here in this nxvium promotional video, started taking classes to become a coach. During this time, oxenberg says her daughter burned through her entire inheritance. Largely, she believes, to pay for those classes. Once she moved to Albany, she became very secretive. The end of last April, a defector called me and said, "You need to save India." Reporter: Oxenberg says this was the first time she heard about that secret sorority. I mean, you must have been out of your mind with worry. I did. There was a period of time, probably a week, where I thought I was going to lose my mind. Reporter: But a month later, a rare opportunity to confront India when her daughter came home for a birthday celebration. How did she look to you? She looked sad, she looked tired. Reporter: She says her daughter had become very thin, a characteristic of many nxivm women, we're told. Oxenberg says India also revealed she had not menstruated in a year. Concerned, oxenberg tried an intervention. I said, "Darling, I believe you're brainwashed." And she said, "I'm not brainwashed." And I said, "Yes, you are." And she said, "No, im not." So it's like we didn't get anywhere. Reporter: Oxenberg says her daughter denied having sex with Keith raniere, but did admit she was branded. I said, "Try to convince me that this is a good thing." And she said, "It's character building." She's over 18 and so legally there's nothing I can do. Reporter: In a letter posted on the group's website, raniere says, "There is no merit to the allegations that we are abusing, coercing or harming individuals." Raniere says that secret sorority is "Not part of nxivm and I am not associated with the group." The letter also says, "Our experts say members of the sorority are thriving, healthy, happy, better off, and haven't been coerced." Federal prosecutors say it's just not so. They say raniere is the head of the secret sorority, and some of the women, far from being healthy or happy, were allegedly coerced into working for free or having sex with raniere. India has not responded to our requests for comment, but she posted a public rebuke on Facebook to anyone questioning her condition, saying, "I'm absolutely fine. Great, actually." She's anything but fine. She's in danger. In my opinion, she's in grave