Lucy Lost.

Set in 1915 in the Isles of Scilly just off the Cornish coast, a young girl named Lucy is raised by a clan of fishermen she knows not to be hers. However, she remembers little else about her past, and as the Great War rages down on the continent, a chance encounter with the mysterious girl her own age soon helps Lucy put back the pieces of her own life’s story and come to better understand her place in the world.