Over the past several weeks, arrests of members from the purported self-help group Nxivm have revealed an underground web of heinous crimes, from sex slavery to pyramid schemes.

Reports and rumors about the groups connections to Hollywood actors were mounting. And on Friday, actress Allison Mack — best known for her roles on Smallville and Wilfred — was arrested on sex trafficking and forced labor charges.

Mack allegedly recruited women into a sex trafficking pyramid scheme within Nxivm. The group's founder, Keith Raniere (known by group members as "Vanguard"), has been accused of standing at the top of said pyramid. He was arrested in Mexico last month on the same charges.

Court filings describe how Raniere used Nxivm as an umbrella company to mask a secret society called "DOS," which blackmailed and branded unsuspecting victims before forcing them to participate in sex acts.

"DOS operated with levels of women 'slaves' headed by 'masters,'" the court filing describes. "Slaves were expected to recruit slaves of their own (thus becoming masters themselves), who in turn owed service not only to their own masters but also to masters above them in the DOS pyramid."

Mack is said to have been at the highest level of the pyramid just below Raniere, actively coercing women into lower levels of the scheme. Raniere supposedly rewarded Mack with money and "other benefits" for every victim she convinced.

In a 2017 Youtube video from the official Keith Raniere Conversations channel, he and Mack discuss "The Authentic Human." It reads now like a chilling preview of the tactics they potentially used to carry out the alleged operation.

"Mack and other DOS masters recruited DOS slaves by telling them that they were joining a women-only organization that would empower them and eradicate purported weaknesses that the Nxivm curriculum taught were common in women," the indictment says.

The women were pressured into providing "collateral" before they could join the elite secret society, providing naked pictures, sensitive information about themselves and loved ones, and even rights to their assets. This blackmail was then used to both keep them in DOS, and maintain its secrecy.

In what is perhaps the most sickening detail of all, the court document says that:

Many DOS slaves were branded on their pelvic areas using a cauterizing pen with a symbol which, unbeknownst to them, incorporated Raniere’s initials. During the branding ceremonies, slaves were required to be fully naked, and a master would order one slave to film the branding while the others restrained the slave being branded.

The indictment does not make clear whether there was any direct relationship between the sex-trafficking pyramid of DOS, and the more public-facing self-help pyramid scheme of Nxivm. The actress is, however, a known co-creator of programs that enlisted other actors for Nxivm's increasingly expensive "empowerment" classes and workshops.

Kristin Kreuk and Allison Mack were co-stars on the WB hit 'Smallville.' Kreuk was also a member of Nxivm for several years but denies involvement with any sex trafficking. Image: warner bros.

Several aspiring and established Hollywood actresses have had varying levels of involvement with Nxivm. Mack's Smallville co-star, Kristin Kreuk, was a member of Nxivm for several years but denies involvement with any sex trafficking or even knowledge of DOS. Another actress, Sarah Edmondson, has previously spoken out about the abuses she suffered within DOS and corroborated Kreuk's statement.

Mack was scheduled to appear in court on Friday. Raniere will appear in court at a later date. If convicted, they face anywhere from 15 years to life in prison.

“Today we announce an additional arrest, and an indictment, in a case that brought to light an inconceivable crime,” said FBI Assistant Director-in-Charge Sweeney about Mack's arrest. “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."