Mafalda is nine years old. She wears glasses with thick yellow lenses and knows “The Baron in the Tree” by Italo Calvino by heart, and she adores her cat. She has a rare retinal disease, and soon she’s facing complete blindness. She is afraid of ending up in the dark, so she keeps a diary where she writes down what she will no longer be able to do—for example, counting stars, playing football with the boys, or climbing the cherry tree in the school yard. She loves that tree, which has become her only refuge, and from afar she greets it like her best friend. But the trouble is that with each day the distance between the spot where Mafalda can still make out the outline of the tree and the very cherry tree gets shorter—meaning darkness is already very close…