Explosives, in Polly Banks' case, are her P's and B's (her own initials, as the shrink points out), and her trouble is that she can't say them without stuttering. This takes place the year she's eleven and pretty much overcomes the problem; moving to yet another town and school, she impresses tough Sis Hawkins with her athletic ability and then, bolstered by the friendship, helps her battle a neurotic, tyrannical teacher who has it in for independent, nervy Sis. In between are talks with Mom and with the shrink--none go very far. Low-powered, still we wouldn't call it a dud.