""Be very careful, sir " the young officer warned. "Colonel Lavedrine is a guest of this house, and this nation. I can hardly believe that any Prussian would be so foolhardy to doubt his word. Every man in Paris has heard of his capacities. I see no reason why this Professor Kant of yours should not have heard of them, too."""Lavedrine sat back in his seat, a thin smile on his lips, stroking his chin with his thumb and forefinger. He seemed to be scrutinizing me, curious to hear what my reply would be."""If Colonel Lavedrine can prove the truth of what he says," I returned, glancing between my accuser and the man I had accused, "I will apologize with all my heart. And if that apology does not satisfy him," I added, leaning back in my chair, shrugging my shoulder, "the prison cells are waiting for Prussians such as me, who are obliged to have guests such as you """I suddenly realized that the room was silent."It is 1807 and Napoleon's army has swept over Prussia, leaving in its wake a conquered land occupied by the French. Local magistrate Hanno Stiffeniis has retreated to his home in the countryside in the hopes that he can keep himself away from the scrutiny of the occupying forces. But when Serge Lavedrine, Paris's famed criminologist, requires his services, Stiffeniis has little choice but to accept. Three children have been found massacred in their beds. Their mother has disappeared without a trace. Terrified by the gruesome murders, the local townspeople have become convinced that the crimes are the work of the local Jewish population. The ghetto has been closed off, but the crowds gathered in the streets are desperate for justice of any kind. The French authorities want nothing more than a quick resolution and an end to the hysteria that has gripped the town. Stiffeniis has his own reasons for accepting the case. The victims' father serves as a soldier in remote Kamentz, where the resistance to Napoleon's occupation is already developing. If Stiffeniis cannot discover the whereabouts of the mother and the identity of the murderer in time, he risks exposing the Prussian rebellion to the French before it has the strength to succeed. To succeed he must once again put to use the powers of deduction learned from his late teacher, the famed philosopher Immanuel Kant. Michael Gregorio's internationally bestselling debut, "Critique of Criminal Reason, "was hailed by critics across the world and named one of "Playboy"'s Best Books of 2006. Now its sequel, "Days of Atonement, "marks the thrilling return of one the most talented new voices in historical fiction.