A plane crashes in France. All passengers are killed except a baby girl. The premise sounds unbelievable and silly. But the more you read, the more plausible it becomes. 
 A custody battle ensues between possible grandparents from the rich de Carville family and possible grandparents from the poor Vitral family, each with plausible claims that the baby is theirs. Custody of Lylie, as she comes to be called, is awarded to the Vitrals, who are also taking care of their grandson, Marc. After 18 years, Marc has developed an attraction for Lylie, who does not look or act like the rest of the Vitral family. 
 After the custody battle, the de Carvilles hire a private eye, Credule Grand-Duc, to keep investigating the case. He uncovers many clues but mostly dead ends in a maddening 18-year search. Throughout the novel, Marc is reading passages from Grand-Duc's journal about the case. That is primarily how we learn about validity of the competing families' claims. 
 The story is mysterious and suspenseful. Bussi intentionally frustrates the reader by withholding crucial information. For example, after Grand-Duc writes that he arranged for a secret DNA test, he doesn't record in his journal what the results were. Instead he simply writes about how shocked and dismayed he was by the results. Much of the book is like that--one tease after another. The teasing starts out fun but becomes tedious and annoying. 
 Bussi wants the readers to root for Marc and Lylie's relationship. Several of the main characters hope that Marc and Lylie aren't actually brother and sister so that they're love affair will be acceptable. However, the whole concept grossed me out. Even if they are not biological siblings, they still grew up together. Their romance didn't work for me. 
 Some of the prose is stilted and the word choice is uneven, which I assume is because of the translation. 
 If you want to read a clever mystery that doesn't start with a murder, this book will fit the bill. There's enough intrigue, clues, and red herrings to motivate you to keep reading. But overall, the purposeful withholding of information got old. I wanted the book to end. For that and the incest/yuck factor I'd give this book a two-star rating.