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 as 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. . . .