When Scout, a tiny robot at Bellwether Creek Library, suddenly starts crashing into the same wall, Gid Ralston is sure something is broken. But with Tess, Bram, June, and the clever digital companion Axo beside him, Gid discovers a much stranger mystery: Scout isn't seeing the wall the way people do. Reflections, light, and tricky surfaces are fooling its sensors—and sending the little robot completely off course. As the children follow one surprising clue after another, they learn that solving a mystery isn't about having the fastest answer. Sometimes, the best discoveries begin with one simple question: What is really happening?