To hold her life together at Cirey, Émilie had to manage a number of risks. First she feared disgrace, banishment and the loss of her children. At this time in France, adultery was a crime—but only the woman was punished! If the Marquis du Châtelet should ever decide that Émilie was disgracing his noble name, he had the legal right to repudiate her, strip her of the means of existence, banish her (to a convent, if he were generous), and never allow her to see her children again.

At Cirey, Émilie was living with one of the most entertaining men in Europe, who was a darling of theatregoers and of society in general—but she was also consorting with a former criminal. Because of Voltaire’s banned book, The Philosophical Letters, King Louis XV held the warrant for his arrest in a drawer at Versailles and could reactivate it at any time. If Voltaire were thrown into prison or exile, or tempted away to an illustrious ‘philosophical’ court (such as that of Prince Frederick of Prussia, who was determined to get him to Potsdam), or lured to Paris by the Comédie Française, or to Holland to publish the books he couldn’t print in France, her beautiful world of love and learning would collapse.

In 1737, Émilie helped Voltaire with experiments that he made in order to write his essay ‘On the Nature and Propagation of Fire’ and realised that if she entered the competition (an act unheard of for a woman) her conclusions on Fire were bound to differ from his. The idea of doing so became irresistible: she wrote it at night and in secret, and asked her husband to submit it to the Academy of Sciences.

At the beginning of the opera, which takes place over a single day in 1738, Émilie realises that she has created yet another risk in her life: when Voltaire discovers her secret he is bound to be hurt, probably by her having written the essay in competition with his, and certainly by the fact that she’s deceived him about it for months. And suddenly Maupertuis arrives at Cirey with the results …