Set in 17th century France at the court of the Sun King, King Louis XIV, the young, colony-raised, naive Mademoiselle Marie-Josèphe de la Croix is the lady-in-waiting to King Louis XIV's niece. Her brother, Father Yves de la Croix - a natural philosopher and explorer - has recently returned from a mission commissioned by the king: to bring back the endangered sea monster whose flesh is rumoured to give the consumer immortality. Father Yves brings back two specimens: one, a dead male sea monster covered in sawdust and ice; the other, a live female sea monster placed in the Apollo fountain in the Palace of Versailles. Acting as her brother's assistant, sketching the dead sea monster's dissection, and caring for the live specimen, Marie-Josèphe soon realizes the creature is not a sea monster, but a sea woman. Thus, Marie-Josèphe tries to convince the others at court, including her brother, that the sea woman is intelligent and hopefully free her. Unfortunately, only Marie-Josèphe can understand the sea woman (now called Sherzad)and her musical way of talking. As a result, the court - especially the men - ignore her. They bleed her for hysteria, the Pope openly shows outrage over the impropriety of her composing a cantata, and several court men harass her on the King's hunt. At the same time, her slave Odelette (really called Haleed) struggles to gain her freedom. Only, the stoic Count Lucien believes Marie-Josèphe about the sea woman, calmly taking the sea woman and Marie-Josèphe's scientific endeavors in stride. In order to save her own life, Sherzad, the sea monster, offers the king the location of a sunken treasure ship in return for her freedom. But despite the discovery of Spanish gold found from the wreck, the king intends to keep Sherzad and eat her, the lure of immortality being too strong. Marie-Josèphe and Count Lucien - who she has fallen in love with - plot secretly to release Sherzad, defying the pope, their king, and her brother. Their attempt fails, but Yves - finally realizing the Sherzad's conscientiousness and its repercussions on his actions - aid them in finally releasing Sherzad. In the end, Marie-Josèphe and Count Lucien are exiled, but Sherzad, who had declared vengeance on all humanity, showers them with forgotten sunken treasures in gratitude.
Marie-Josèphe de la Croix - Lady-in –waiting to King Louis XIV’s niece. Younger sister of Father Yves de la Croix. Convent-raised and at first, naïve. Amateur composer and lover of mathematics. Assistant to her brother in his scientific endeavors (mainly as a sketcher of specimens). Also, shares her brother’s interests in natural philosophy. Befriends the sea monster, later called Sherzad. Marie-Josèphe is the only one able to understand the sea monster, and thus, Marie-Josèphe becomes her translator.
Father Yves de la Croix - Marie-Josèphe’s older brother. A Jesuit priest and King Louis’s natural philosopher. Recently returned from an expedition commissioned by the King to find the legendary sea monster – the possible key to immortality. Stuck between his religious obligations, his scientific endeavors, and his own pride. Later revealed to be a bastard son of King Louis.
Count Lucien de Chretien - A dwarf. Open Atheist. King’s Louis’ most trusted advisor. Epitome of etiquette. Marie-Josèphe’s love interest. Stuck between his kindling feelings for Marie-Josèphe and his duty to his beloved King.
Sherzad (the sea creature/sea woman) - One of the last sea monsters in the world. Captured by Father Yves de la Croix and caged in the Apollo fountain in the Versailles for King Louis XIV. Flesh is rumoured to make the eater immortal. Saliva can heal wounds, though this fact is not realized by the other characters. Has two tails, tangled hair, and a gargoyle face. Enchanting voice - the music of which is her way of communicating. Can only communicate with Marie-Josèphe. Later vows vengeance on all humanity. 
The depiction of alien life - The sea monster's credibility is evident by details such as her ability to communicate. The sea monster's singing speech, acts like a dolphin's own speech - the sound echoes in the ocean. Also, like a dolphin the sea monster can use sound waves and their reverberations to discover what may be inside an object. These facts and the other characters' careful scientific approaches help to make sea monster a well-rounded alien species.
The effect of political and religious beliefs on scientific endeavors - Marie-Josèphe has to write a letter to a foreign mathematician in secret. Pope Innocent at one point reprimands Father Yves for his interests in scientific studies, instead of being devote and pious to the Catholic order. He sentences Father Yves to meditate. At the same time, the Duke of Chartres (the King's nephew), an aspiring chemist, has his interests shot down repeatedly by his parents for his noble birth and title. And the King seeks immortality in the flesh of the sea monster - something all scientists know is basically impossible, and yet something which Marie-Josèphe and Father Yves struggle to tell the King.
Barriers for women pursuing scientific interests - Marie-Josephe is seen only as her brother's assistant, even though she is possibly the better scientist. When she composed music, her music is credited to another composer. When the music is discovered to be hers, Marie-Josèphe is openly rebuked (especially by Pope Innocent XII) for impropriety and abusing her role as a woman.
Cosmos Filmed Entertainment, in association with Lightstream Pictures, will produce a film version of The Moon and the Sun in partnership with the China-based Maodi group. Bill Mechanic of Pandemonium Films, James Pang ("Painted Skin 2"), Paul Currie ("Rampart") and Evergrande's Timothy Mou are also producing. The movie will starr Pierce Brosnan as King Louis XIV; Chinese movie star, Fan Bingbing, as the mermaid; and Bill Nighy as Pere de Chaise (a character created for the movie). Filming will take place Australia this April, with two weeks of filming also planned in Versailles, France. Mechanic wrote the screenplay with the help of Barry Berman, James Schamus and Ellen Harrington. Sean McNamara (Soul Surfer) is set to direct.The $40 million budget was co-financed by U.S. and Chinese sources. The film will be released by Universal's Focus Features in the U.S., while international sales will be handled by Good Universe.