Allison Mack, the actress best known for appearing in the Superman TV show Smallville, was arrested on Friday and charged with helping run a secret society that enslaved women and branded them with the founder’s initials, according to prosecutors. It follows the arrest last month of Keith Raniere, a self-help guru who ran a network of workshops known as Nxivm. Mack, 35, has been charged with sex trafficking and conspiracy, and was due to appear in Brooklyn federal court on Friday afternoon. Richard Donoghue, United States attorney for the Eastern District of New York, said: “As alleged in the indictment, Allison Mack recruited women to join what was purported to be a female mentorship group that was, in fact, created and led by Keith Raniere. “The victims were then exploited, both sexually and for their labour, to the defendants’ benefit.” Actress Allison Mack attends the WB Network's 2002 Summer Party at the Renaissance Hollywood Hotel on July 13, 2002 Credit: Robert Mora/Getty The criminal complaint, alleges that Raniere – who gave himself the title “Vanguard” – set up a series of self-help workshops with five-day courses costing as much as $5000. Women were told that the best way to advance was within a secret group of “slaves” and “masters”. The complaint says Raniere stood at the top of the pyramid and women were expected to have sex with him. Inductees were allegedly required to provide “collateral” such as damaging information about family and friends, nude photographs or rights to assets, which they feared they would lose if they did not go along with the rules. He fled the US last year after The New York Times exposed the organisation. However, he was arrested after being tracked down to a Mexican resort. Keith Raniere was arrested in March Credit: Youtube Mack helped force the women to have sex with Raniere and received financial and other benefits from Raniere in return, prosecutors said. Her lawyers could not be reached immediately for comment. William Sweeney, who is leading the FBI investigation, said: “As this pyramid scheme continues to unravel, we ask anyone who might have been a victim to reach out to us with information that may further our investigation.” Raniere denied the allegations when they were first reported. “Over the past months, there have been extensive independent investigations performed, by highly qualified individuals, and they have firmly concluded that there is no merit to the allegations that we are abusing, coercing or harming individuals,” he wrote on the group’s website.