Feeling ignored and suffering a ""failure of cooperation"" since the birth of a new sister (Muffin), Lily (8) runs away, setting out by train from Scarsdale en route to a Trenton orphanage, taking Muffin with her. When a love-starved woman abducts Muffin from the train, reality sets in; and by the time Muffin is found, Lily is comfortingly aware of her family's love for her--and hers for them. This ""Stepping Stone Book"" has funny, sharply observed dialogue, and a firm grasp of the effects of sibling rivalry. Though the kidnapping and its aftermath are somewhat simplified, the dangers are taken seriously enough to provide both a lesson and a satisfyingly suspenseful story.