Brume, a feisty little girl from Brittany, dreams of becoming a powerful witch. When a thick fog envelops her village, she sets out, accompanied by her best friend Hugo and her pet pig Hubert, on an adventure into the heart of the forbidden forest.

Through this coming-of-age journey, Brume uncovers a mysterious bond with Naïa, a legendary witch, and realizes she must face Ankou, a haunting figure tied to death itself.