What happens when a five-dollar offer meets a box of possibilities? At a neighborhood garage sale, Gid Ralston discovers a tiny silver sensor hidden among old electronics. One buyer sees a bargain. Gid sees a question. With Axo's clever observations, Dad's workshop know-how, and plenty of help-and trouble-from Pippa, Bram, June, and the ever-mischievous Waffles, Gid follows the mystery from driveway deals to a garden invention. Along the way, he discovers that price and value are not always the same thing-and that the smallest, strangest things can become useful when someone takes the time to look closer.