If animals and an occasional plant can aid the human heroes of old-time fairy tales, why not a fire hydrant, street lamp, gas pumps, and phone booths in a modern one? The Stevensons (father and daughter) have just such an assembly bustling about trying to help third-grade Maxwell save the town from washing away when rain swells the water in an old riverbed. Fortunately for the story, it turns out that these contentious, bumbling devices are no help at all, and in the end it's a small, dented oil can who gives Maxwell the much-needed confidence--and, gently prodding, the ideas--that do the trick: the can, held by Max, oils the old dam door's rusty crank, which Maxwell--bravely, precariously--then turns to open the dam. There's a sweet-sad parting at the end when the oil can goes down the river ""to see what there is to see,"" and Maxwell and his dog Linda go home. But the authors' handling of the ego-boosting function of the adventure is perfunctory, and even though Stevenson's drawings are as appealingly human as can be, it's awfully hard to get sentimental over an oil can.