Phil Weaver, a mechanical mastermind, and his friends, Waldo and Buff, are wandering aimlessly through their summer vacation when a karting business falls their way. The kart fad -- racing souped-up vehicles -- hasn't hit Hillandero yet and the boys have an open market. Phil backs out of the business when he realizes that karts in the wrong hands can be dangerous. When a faulty kart falls apart through no fault of Phil's, the acting mayor declared the vehicles illegal and the dangerous races come to a screeching end. Boys enamored of engines will find this karting tale entertaining, and it is less controversial than Summers' earlier books.