It is the summer of 1892, one year since Sophia Tims and her friend Theo embarked upon the dangerous adventure that rewrote the map of the world. Since their return home to Boston, she has continued searching for clues to her parents’ disappearance, combing archives and libraries, grasping at even the most slender leads. Theo has apprenticed himself to an explorer in order to follow those leads across the country—but one after another proves to be a dead end.