The Prologue sets the scene—medieval France in the year 1242—and introduces us to our anonymous narrator. This nameless man is sitting in a packed inn on a stormy night, looking for a story. He finds one. It turns out that the powerful young King Louis is preparing to go to war against an unusual enemy: three children and their dog. One of the people at the narrator’s table, a beer-maker (or brewster) named Marie, says that she knows one of these children very well, and that she’ll tell her story.

The brewster tells the story of one of the three strange children, a girl named Jeanne. The daughter of peasants, Jeanne seems unremarkable, except for her beautiful dog: a white greyhound with a copper-colored nose, whose name is Gwenforte. As a baby, Jeanne is often left in the dog’s care. This surprises our original narrator, who breaks in to ask if it’s normal for dogs to babysit.

Marie explains: one day, while Gwenforte was guarding baby Jeanne at home, a poisonous adder (a kind of snake) slithered into the house. Gwenforte killed the snake before it could hurt Jeanne. When Jeanne’s parents came home and saw Gwenforte covered in the snake’s blood, they thought she had hurt the baby, and killed her.