The late 1500s and early 1600s saw much of France caught in the grasp of what many would call werewolf paranoia. Certainly many of the most famous cases of lycanthropy occurred during this time. One of the most celebrated was that of Jean Grenier, made worse by the fact that he was just a boy at the time. The saga began when some village girls came upon a boy of about thirteen while walking on the sand dunes. His thickly matted hair, torn clothes and gaunt appearance were alarming but what made them flee were his assertions that he was a werewolf and that he would attack the fairest of them should the sun set.

The incident remained forgotten until Marguerite Poirier, returning from tending her sheep, complained that her companion had scared her terribly. Previously, the boy had claimed to be the son of a priest and that selling his soul to the Devil had given him the ability to change into a wolf. In this form he had killed numerous dogs and at least two young girls, devouring parts of them. On this occasion, Marguerite had gone to her flock and noticed that the boy was not there. She was then attacked by what appeared to be a small, reddish wolf but had successfully fended it off with her stick. The boy was identified as Jean Grenier, the same lad seen by the girls in the sand dunes.

Grenier did not deny the accusations. In fact he seemed eager to provide details, implicating his father in at least one murder. He claimed to have been taken into the forest at night by his neighbor, M. Duthilliare, and introduced to the Lord of the Forest who gave him a salve and a wolf skin. This allowed his transformation and he admitted to killing at least one dog and a number of children, including an infant stolen from its crib. Given that there was only his testimony incriminating his father, the latter was set free.

Unlike other offenders, Grenier was surprisingly spared from death, ostensibly by his age. The presiding official instead, believing that he was suffering from a mental defect and could not therefore be punished, determined that he should spend the rest of his years in a monastery. He died after seven years.