Margaret Blackburn, the renown and attractive English sleuth living in Bermuda, was invited to the chateau of Rosny, in France, near the city of Bourges. She had been asked to investigate the tragic fate of Philippe de Belfort's new love interest, the Countess Diane de Briare. She had fell to her death from the balcony of the bedroom. Some have mentioned suicide, and others claimed that she was sleep-walking. Yet, the coroner reported several unusual findings that made him suspect foul play, such as the rip in the back of the dress and the two missing buttons. Margaret became convinced that this was not an open and shut case. Furthermore, the victim's sister, Isabelle, had disappeared. Her estranged husband, Julio, the Spanish artist, had come back with impossible demands, and many threats. The behaviour of the Mesnier, a young couple newly settled in the area, was hard to understand. Then, there was the shrink, the pharmacy delivery boy, and, of course, the butler. Did this one do it, for a change?
The only thing Margaret knew, when she had accepted the invitation, is that Estelle Lebreton, the journalist, Pierre Maximilien, her husband, the editor, and Igor, their lab, were beyond suspicion.