In short, from a review:
Lévy, a small-scale livestock dealer from Boulay traveled to nearby Metz on the eve of the Jewish New Year in 1669 to purchase a shofar for the holiday. Shortly afterward, he was summoned to Metz to answer questions about the disappearance of a Christian child who had vanished on the road from Boulay to Metz on the day of Lévy's travels. Relying on trial documents and the journal of an anonymous Jew, Birnbaum painstakingly reconstructs the contradictory, hateful, and irrational testimony of the prosecution's witnesses and the vehement defense of the accused, who was tortured...the intendant of Metz, who represented the king, protected the Jews from would-be rioters riled up by the trial. Furthermore, the king's Council of State prohibited the Metz parlement from carrying out its death sentence. The king himself prohibited future trials for ritual murder and forbade even the belief in the charge. Nonetheless, as Birnbaum relates, new accusations of ritual murder arose well into the modern period. Even Abbé Grégoire, who championed the emancipation of the Jews, refused to dismiss the possibility that a few Jews in the past had committed ritual murder. Birnbaum's focus, however, is not on Grégoire or even on the Damascus affair, but on the intense role that blood libel played during the Dreyfus affair.