Deep in his terrifying realm underground, the cold and forbidding Goblin King casts a dark shadow over nineteen-year-old Liesl. Her grandmother had always warned her to follow the old laws, for every year on the longest night of winter the Goblin King will emerge into the waking world in search of his eternal bride. Sensible and plain, Liesl knows it's her duty to keep her beautiful sister safe from harm, but she wishes only to indulge in her wild, captivating music, composed and played in secret in the Goblin King's honor.

When her beautiful sister Käthe is stolen by the Goblin King, Liesl knows she must set aside her childish fantasies to journey to the Underground and save her. Drawn despite herself to the strange, beautiful world she finds--and the mysterious man who rules it--she finds herself facing an impossible choice. With time and the old laws working against her, Liesl must discover who she truly is before her fate is sealed.