Never stay too long in one spot,"" Sim's mother Simolina had said, and at his urging the three friends set out on their travels, stacked like a pyramid (Sim on Suzy on Sansom). They pass over the desert, pause at the edge of the sea--but where is Sim? Investigating a strange object, Samson and Suzy are suddenly borne aloft--the object is an umbrella--to alight at last in a land Of ice and snow where two Eskimo children rescue the stricken Samson and take him to their igloo. Their well-read father (""at least a hundred books""), realizing the elephant's plight, immediately produces a big red balloon and some strong cord; Sim is found (he had fallen asleep in Samson's ear) and the three take off. Once home, they are welcomed by their friends (Samson to the water hole, Suzy to a fresh harvest) and Sim wonders--could any other spot be as good as this? A passing leopard provides another chance and Sim is off and away on its back--""Of course Simolina was right."" If Sim were more characteristically a flea, this blend of concrete, very accidental improbability and bemused whimsy would make its point more surely; as it is, the diverse elements don't quite coalesce except in the very appealing illustrations.