Twelve-year-old Caspia hates big cities, especially one as busy as New York. So she isn't thrilled by the news that her parents are taking her to stay in Brooklyn. It's summer devouring bad luck! But everything changes when Caspia discovers a bundle of letters, hidden in an old chest of drawers. They belonged to two sisters who lived there long ago. Each letter contains a 'green' riddle, with clues leading to a different plant. Caspia sets out to solve the riddles and as she does, she meets friends she could never have imagined and discovers that anywhere can feel like home, if you are just brave enough to put down new roots.