Lethal Beauty, set in 1787 at the Louvre in Paris, opens with a ghastly discovery. At the biennial exhibition of paintings and sculptures, the portrait of a recently deceased countess is vandalized. Its painter accuses a colleague, who is soon stabbed to death. Anne Cartier is drawn to investigate the crime by her deaf friend Michou, a pupil of the murdered man. The circle of suspects widens to include the countess's elderly husband, the Comte de Serre, who had commissioned the portrait. Yet another suspect is an Italian art dealer, who may have known the countess too well and has reasons both to love and to hate her. But at the centre of the mystery is a master extortionist ensnaring the participants. Anne, her husband Colonel Paul de Saint-Martin, and his adjutant Georges Charpentier pursue the investigation from the Louvre's apartments and studios into the streets and sewers of Paris and beyond, to the count's country estate near Fontainebleau.