The worst person in the world ""lived all alone in a terrible mess. . . in an old house in a yard full of poison ivy."" And when children in a field ask old Mr. Worst if he's seen their lost baseball--"" 'Certainly not,' he said, looking right at it."" Then the worst person in the world meets the ugliest thing in the world (a sort of pastel-spotted, one-horned stegosaurus)--but Ugly, convinced that ""if you've got a pleasing personality that's all that counts,"" follows the worst home. cleans the place up, and decorates it for a children's party. The worst, fed up, orders Ugly, children, and party out and away. . . and then, alone in the usual but suddenly less satisfying gloom, reconsiders. A mean old character is always more interesting than a kindly one, and you can trust Stevenson to make the worst (as he frequently calls him) as grumpy, sour, and lonely as anyone could wish. He is also touching, and his inevitable reform is effected with wit, and without violating the old codger's established gruff manner.