Actress Allison Mack has pleaded guilty in a case involving a cult-like group based in upstate New York. Mack entered her plea to racketeering charges on Monday, shortly before federal jury selection was scheduled to start in Brooklyn federal court.

The trial is expected to detail sensational allegations that the group, called NXIVM, recruited sex slaves for its spiritual leader, Keith Raniere. Authorities said the women were branded by a surgical tool with a symbol that resembled Raniere's initials.

Prosecutors accused Mack of helping Raniere recruit women to a secret sub-society within the group. Mack is best known for her role as Chloe Sullivan on the series "Smallville." The character was a close friend to Superman on the show.

Allison Mack seen May 4, 2018, in New York City. Getty

Mack has said in an interview that the group emphasized self-discipline and self-empowerment and she likened the branding to getting a tattoo, but cooler. The defense said the women were never abused.