Beneath the city lies a secret the world was never meant to see. Lena Marlowe thought she was just another high school senior—until a cryptic heirloom unlocks the hidden passage to the Thirteenth Circle, a forgotten realm of magic, riddles, and dangerous creatures. But the Circle is crumbling. A dark figure named Riven is bent on seizing its power, threatening both the underworld and the city above. To stop him, Lena must brave the Circle's trials and uncover the truth about her family's mysterious ties to its ancient magic. With a loyal best friend, a reluctant guide, and a fierce warrior who may or may not trust her, Lena is thrust into a battle that will test her courage, her identity, and her heart. Fans of The Mortal Instruments and A Darker Shade of Magic will be swept into this thrilling urban fantasy full of mystery, danger, and self-discovery.