Rich heiress Ava is cruelly betrayed by her boyfriend and best friend on a luxury cruise, then pushed into the deep sea by her own brother. On the verge of death, she accidentally awakens Kael, a sealed thousand-year-old merman king, surviving the fatal fall and unlocking her hidden Tideborn bloodline. Bearing the identical face of the deceased sea queen, she is imprisoned in the deep sea by the obsessed Kael as a substitute. Torn between love and hatred, Ava breaks free from bondage, exposes the shocking conspiracy of her brother and the sea witch, and uncovers the truth of her mother’s tragic death and stolen bloodline. She shreds her doomed fate as a substitute, takes revenge across land and sea, and finally gains complete freedom.