Chet Gecko loves a good mystery. Almost more than he loves his fee - stinkbug pie. So when fellow fourth grader Shirley Chameleon asks him to find her missing brother, Billy, Chet expects the case to be as easy a pie. But Billy's disappearance is part of a larger plot, one that involves the Rat Sisters, a riddling junkyard dog, and a vicious Gila monster named Herman. If Chet doesn't solve the case fast, the entire school could be humiliated. Worst of all, Chet might not get his fee. And Chet's hungry. . . .