When her father, a Maine lighthouse keeper, is transferred to a station on a barren island far offshore, Sarah is quick to note how much her mother misses the flowers she used to grow in her garden on the mainland. Determined to reverse her mother's melancholy, the girl hatches a plot to put soil in the cracks and crevices of the ledge and to plant seeds there. Lo and behold, they bloom, delighting not only Sarah's family but also the local fishermen. The book is based on a true story about the light at Mount Desert Rock around the turn of the nineteenth century.