Allison Mack. Photo: Mary Altaffer/AP/REX/Shutterstocl

A teary Allison Mack pleaded guilty to two federal counts Monday in the NXIVM sex-cult case.

“I have come to the conclusion that I must take full responsibility for my conduct and that’s why I am pleading guilty today,” said a choked up Mack, who admitted to one count of racketeering conspiracy and one count of racketeering.

Mack attended court in dark relaxed-fit pants and a creamy mock-neck sweater. She kept her hair in a bun and sported leopard sneakers, as she had at her last court proceeding.

Her casual dress stood in stark contrast to the gravity of the situation, as she faces up to 20 years in federal prison on each count.

At the beginning of her allocution, Mack explained in part what drew her to NXIVM. Many of the members were “wonderful people and some of whom, I now realize, were not.”

“I joined NXIVM … to find purpose,” she said of the group, which was headed by co-defendant Keith Raniere. “I truly believed I found a group of individuals who believed as I did.”

“I believed Keith Raniere’s intentions were to help people,” she said. “I was wrong.”

Prosecutors allege that NXIVM, an Albany-area organization that offered costly self-help classes, contained a secretive sect called DOS that “operated with levels of women ‘slaves’ headed by ‘masters.’”

After Mack’s arrest last year, prosecutors said that she served as a “master” under NXIVM founder Keith Raniere, recruited slaves, and “directly or implicitly required her slaves … to engage in sexual activity with Raniere.”

“I was a member of a secret society,” Mack also admitted in court, saying she tried to recruit other women to join DOS.

She said she obtained “collateral” embarrassing information about several women so they would go along with NXIVM’s demands.

“I’m very sorry for the victims of this case,” the Smallville actress said. “I’m very sorry for who I’ve hurt through my misguided adherence to Keith Raniere’s teachings.”

“I know that I am and will be a better person because of this,” Mack said.

Raniere, who is charged with sex trafficking and possessing child pornography, allegedly gave Mack “financial and other benefits” in exchange for her recruitment efforts, prosecutors said.

Mack and her lawyer declined to comment outside the courthouse as she moved through the throng of photographers, eventually getting into a silver Toyota SUV.

The proceeding came in the wake of recent courthouse theatrics and ongoing expectations that Mack would take a plea before trial.

Last week, Mack and Seagram’s liquor heiress Clare Bronfman, who is also charged in the case, had a gushing BFF-esque reunion, with long hugs and cheek kisses before a proceeding in the case.

Judge Nicholas G. Garaufis decided during this prior proceeding to keep jurors’ names secret, including after the trial, and to “partially sequester” them, which means they will be transported to and from the courthouse by U.S. Marshals on trial days.

Garaufis’s decision was unusual, considering this level of anonymity is typically reserved for dangerous defendants, such as Mexican drug lord Joaquín “El Chapo” Guzmán, not wayward stars and heiresses.

The week before, Bronfman nearly fainted in court after it was revealed that celebrity lawyer–cum–accused fraudster Michael Avenatti had negotiated with prosecutors for her.

This is a developing story.