For two years, Oriana Paredes has been a spy among the social elite of the Golden City, reporting back to her people - the sereia - sea folk banned from the city's shores. When her employer and only confidante decides to elope, Oriana agrees to accompany her to Paris. But before they can depart, the two women are abducted and left to drown. Trapped beneath the waves, Oriana survives because of her heritage, but she is forced to watch her only friend die. Vowing revenge, Oriana crosses paths with police consultant Duilio, a seer, whose gifts have led him to Oriana.