In the dead of the winter of 1940, Hitler decided to return from its burial place in Vienna the ashes of Napoleon II, known as the “Aiglon,” the only son of the emperor Napoleon. The gesture was intended to win the support of the French people, but only managed to precipitate a political crisis at Vichy, where Marshal Pétain ordered the pro-German Deputy Prime Minister Pierre Laval arrested. Based on new research and previously unknown documents, the author, historian Georges Poisson, at last sheds light on an incident most historians—including Robert O. Paxton—have been at a loss to explain.