Watch the trailer for Escaping the NXIVM Cult: A Mother's Fight to Save Her Daughter, based on Catherine Oxenberg's book documenting her fight to save her daughter from the cult. Sara Fletcher, who plays the former Smallville star, bears an uncanny resemblance to Mack. "Are you ready for your NXIVM transformation?" Watch ET's exclusive trailer above to get the full experience. The TV movie premieres Sept. 21.