The summer before sixth grade, eleven-year-old Margaret Simon finds her world uprooted when her parents announce they're moving from their beloved New York City apartment to a house in the unfamiliar suburbs of Farbrook, New Jersey. Leaving behind her doting paternal grandmother, Sylvia, Margaret is filled with a mixture of apprehension and excitement. It is during this time of immense change that Margaret begins her private, earnest conversations with God, starting each one with a simple, "Are you there God? It's me, Margaret." She confides in Him her deepest worries and hopes, especially about fitting in and the bewildering changes happening to her body.
Upon arriving in Farbrook, Margaret quickly falls in with Nancy Wheeler, a confident and seemingly worldly new neighbor. Nancy introduces Margaret to her inner circle, Gretchen Potter and Janie Loomis, and together they form the "Pre-Teen Sensations" club. Their secret meetings are a whirlwind of hushed discussions about all the things Margaret is desperate to understand: boys, bras, and the most anticipated, yet terrifying, milestone - menstruation. They even practice chants to "increase their bust" and eagerly await their first periods, buying sanitary napkins in preparation, hoping to be the first among them to become "women."
School begins, and Margaret's teacher, Mr. Benedict, assigns a year-long research project. When he learns that Margaret's parents, being of different faiths - her mother Christian and her father Jewish - have chosen to raise her without a formal religion, he suggests she make religion her project. This sparks Margaret's quest to find a faith, attending Rosh Hashanah services with her grandmother, and later, Christmas Eve service with Nancy's family. Yet, despite the beauty of the music and the rituals, she doesn't feel God's presence in any organized worship. It is only in her quiet, solitary prayers that she feels a true connection.
The pressures of adolescence mount. Margaret feels a constant ache of wanting to be normal, to catch up to her friends who seem to be developing faster. She stuffs her bra with cotton balls, desperately wishing for breasts, and grows increasingly anxious as months pass without her period. Her jealousy flares when Gretchen gets hers, and then, most surprisingly, Nancy, who had previously lied about already having started. Margaret attends her first party, experiences her first kiss during a game of Spin the Bottle, and navigates the complexities of crushes and social hierarchies, all while still feeling a step behind her peers.
Family dynamics add another layer to Margaret's journey. Her mother reveals she is estranged from her devoutly Christian parents, who disowned her for marrying Margaret's Jewish father. This revelation brings a new understanding of her parents' decision to let Margaret choose her own religious path. As the school year draws to a close, Margaret grapples with her research project, ultimately deciding that she isn't ready to commit to a specific religion. Her personal connection with God, however, remains her steadfast confidant.
Finally, as summer approaches, Margaret gets her first period. It's a moment of immense relief and joy, a sign that she is, indeed, normal. This long-awaited milestone, combined with her ongoing spiritual exploration, brings a sense of quiet understanding. She realizes that some things come in their own time, and that patience, and her continued, honest conversations with God, will guide her through the challenges of growing up.