While her friends are spending their summers having pool parties and sleepovers, twelve-year-old Carolina -- Carol -- is spending hers in the New Mexico desert, helping her parents move her grandfather into a home for people with dementia. At first, Carol avoids prickly Grandpa Serge. But as the summer wears on, Carol finds herself drawn to him, fascinated by the crazy stories he tells her about a healing tree, a green-glass lake, and the bees that will bring back the rain and end a hundred years of drought. As the line between magic and reality starts to blur, Carol must decide for herself what is possible -- and what it means to be true to her roots.