Reeling from her mother's death, sixteen-year-old Bree Matthews seeks a fresh start at a residential program for gifted students. Instead, she is plunged into a hidden world of magic and danger after witnessing a supernatural attack. Her encounter with a 'Merlin' awakens her own latent magic and unearth a buried memory linked to her mother's demise. Bree vows to uncover the truth, embarking on a perilous journey that leads her to infiltrate the Legendborn—a secret society of warriors descended from King Arthur's knights. Navigating their enigmatic ranks alongside Nick, a fellow outsider, Bree confronts the mysteries surrounding the Legendborn and her mother's untimely death. As the society's ancient prophecies come to light, foretelling a magical war, Bree must make a choice that will shape her destiny and that of the Legendborn.