Thirteen-year-old Salamanca Tree Hiddle, known as Sal, is traveling from Ohio to Idaho with her grandparents, in search of her mother. Along the way, she tells them the story of Phoebe Winterbottom, who received mysterious messages, met a "potential lunatic," and whose mother disappeared. Beneath Phoebe's story is Sal's story and that of her mother, who left on day for Idaho and has not returned. Sal has less than a week to get to Idaho in time from her mother's birthday and bring her back. Despite her father's warning that she is fishing in the air, Sal knows this journey is the only chance she has for reuniting her family.