When Rena and her family arrive in Colonia Le Baron, a secluded polygamist Mormon settlement in Mexico, they are commanded to relinquish all their earthly possessions and devote themselves to the doctrines of the LeBaron brothers, Ervil and Joel. However, as the brothers' insatiable thirst for power ignites growing discord, the community fractures, and Rena's family aligns with Ervil. As his teachings take a harrowing turn towards violence, Rena witnesses the transformation of devoted followers into ruthless killers, indoctrinated to carry out brutal acts. At just 16 years old, Rena becomes Ervil's 13th wife, groomed to serve as one of his so-called 'holy assassins'. After being coerced into committing murder against a rival polygamist, Rena miraculously escapes conviction, yet her fear for her life and her daughter's safety becomes palpable. When Ervil is unexpectedly arrested, Rena seizes the opportunity to escape the oppressive settlement, bringing her daughter and other loved ones with her. Driven by her harrowing experiences, she vows to help others break free from the confines of a life she never wanted.
