A mysterious voice has been speaking to Louise in her dreams. She and her brother Merwin are Sycamore seeds, who hope to one day set down roots and become big trees. But when a fire forces them to leave their mama tree prematurely, they find themselves catapulted into the unknown, far from home. Alone and unprepared, they must use their wits and imagination to navigate a dangerous world--filled with dinosaurs, meteors, and volcanoes!--and the fear of never finding a safe place to grow up. As the mysterious voice gets louder, Louise comes to realize their mission in life may be much bigger than either of them ever could have imagined!