Paris, 1885. Aubry Tourvel, a nine-year-old girl, comes across a wooden puzzle ball on her walk home from school. She tosses it over the fence, only to find it in her backpack that evening. Days later, she starts to bleed to death. When medical treatment only makes her worse, she flees to the outskirts of the city, where she realizes that the very act of movement keeps her alive. Her condition won't allow her to stay anywhere for longer than a few days nor return to a place she's already been. But the longer Aubry wanders, the clearer it becomes that the world she travels through may not be quite the same as everyone else's.