Desperate to find the key to immortality, King Louis XIV (Pierce Brosnan) decides to abduct a mermaid (Bingbing Fan) to steal her potent life force. Unfortunately for him, things become complicated when his long-hidden illegitimate daughter Marie-Josephe D'Alember (Kaya Scodelario) discovers the magical creature. The two ladies quickly form a strong bond, and as the King's desire for immortality intensifies, they realize that they must work together to stage an impossible escape. Sean McNamara directs this film based on Vonda N. McIntyre's novel, The Moon and the Sun.