"An Anonymous Girl" is a psychological thriller novel written by Greer Hendricks and Sarah Pekkanen. The story follows Jessica Farris, a young woman who participates in a secretive psychology study led by the enigmatic Dr. Lydia Shields. As Jessica becomes more involved, she discovers unsettling truths about the study and herself. The novel explores themes of morality, manipulation, and the complexities of human relationships. As Jessica navigates the challenges posed by the study, she finds herself entangled in a web of deceit and danger, leading to a gripping climax that keeps readers on edge.