Set in the late 1960s, the plot follows three young women, Leslie "Lulu" Van Houten, Patricia "Katie" Krenwinkel, and Susan "Sadie" Atkins, who become fervent followers of the enigmatic Charles Manson. As they are drawn deeper into Manson's manipulative and charismatic influence, they find themselves living within the confines of the Manson Family compound. The narrative unfolds through flashbacks and present-day interactions, mainly focusing on how Manson's persuasive techniques and promises of a utopian society lure the women into his control. His apocalyptic prophecies and extreme ideologies further compound their devotion, isolating them from the outside world.

Years later, the women are imprisoned for their involvement in Manson's notorious crimes. Karlene Faith, a graduate student, is assigned to work with them as part of a social experiment aimed at rehabilitation. Through her sessions with Leslie, Patricia, and Susan, Karlene attempts to deprogram them from the psychological grip Manson still holds over their minds. These sessions reveal the psychological complexity and the emotional turmoil that the women continue to endure. The story delves deeply into themes of manipulation, control, and remorse while exploring the long-lasting impact of Manson's influence on his followers. The plot highlights their gradual realization and the painful journey towards understanding their actions.