Mercure takes place in 1923, and is almost wholly set on the tiny imaginary island of Mortes-Frontières, just off the Cherbourg peninsula in France, which is inhabited by 23-year-old Hazel Englert and 73-year-old Captain Loncours, along with several servants. Loncours saved Hazel's life in a World War I coastal bombardment five years before, and, telling her that her face is hideously disfigured, in effect has held her prisoner on the island ever since. She is in fact very beautiful, but as Loncours has banned any mirrors or other objects that could reflect that beauty, she believes him about her appearance and thinks that a reclusive life is better than a public freak show. And as Loncours has saved her life, she sees him as a kind of father figure, and although she dreads it when he comes into her bed, she feels forced to allow him regular sexual favors.
This is obviously another of Amélie Nothomb's prison situations, and Loncours is another of her monsters. When Loncours believes that Hazel is a little sick, he calls in nurse Françoise from the mainland, who has to undergo a search for mirrors or pens on her person, etc, but as Loncours is extremely rich and pays the people he employs very handsomely indeed, he hopes that he can buy the silence of Françoise, who is not allowed to ask Hazel any questions that have no bearing on any immediate health concerns she may have. But Françoise not only has a conscience, but is also very astute, and when she pretends that Hazel still has non-existent health problems, she is not concerned about the extra money her daily boat trips to the island will bring her, but about how she can convey the truth to Hazel, perhaps especially because a friendship is developing between the two young women.
One day when Loncours is away on the mainland - shortly after Françoise has transgressed gender norms of the day by having a cognac in a bar, where she learns of the suicide of another woman of Loncours's twenty years before - Françoise raids one of his drawers and finds a photo of the woman, Adèle, who looks remarkably similar to Hazel. And on his visit to the mainland, Loncours learns that Françoise has been buying a thermometer every day and hiding the mercury (for its reflective qualities) in Hazel's room. Mercury is also the messenger of the gods in Roman mythology, and the ancient symbol of messengers is the caduceus, which is very similar to the Rod of Asclepius, associated with medicine: Françoise, of course, is a kind of heavenly messenger from the world of health.
So Françoise becomes the second prisoner on Mortes-Frontières, and must devise a plan to escape from the island with Hazel. But although it's obvious that Loncours is immensely self-deceived, Hazel's self-deception might also cause a brief problem. And Nothomb was so indecisive about closure that she provided two endings.
Mercure wheels out the familiar Nothombisms - entrapment, Kierkegaardian religious obedience, Sartrean mauvaise foi, the hell of other people, angels and monsters, youth and age, beauty and ugliness, lost innocence, intense female friendships, etc - but every one of her books is very different from the other, and I see this as one of her best, in spite of a few oddities: why can't Hazel feel her non-existent deformity, and why is it so easy for the 'angels' to escape from the human bulldogs in the first ending? Very minor niggles, to be sure.
As yet, there is no English translation of Mercure.