In 1407, Louis of Orleans was murdered by a band of masked men. The crime stunned and paralyzed France since Louis had often ruled in place of his brother King Charles, who had gone mad. In charge of the investigation was the Provost of Paris, Guillaume de Tignonville, the city's chief law enforcement officer --- and one of history's first detectives. As de Tignonville began to investigate, he realized that his hunt for the truth was much more dangerous than he ever could have imagined.