A pint-sized Robinson Crusoe in Central Park story about a teen-ager, Jay-Jay, who runs away from his drunken, violent foster mother in Harlem. Dogs are a man's best friend so it is no surprise when Jay-Jay finds Shadow, a sickly pup whom he nurses to health in the tree house he builds in the deserted northwest area of the park -- usually a mugger's no-man's land. A man's home is las castle and Jay-Jay's is replete with ladder, oven and roof -- the only threat (after Jay-Jay destroys his school records) being Elmo, a junkie rip-off artist who roams the park looking for Jay-Jay. Elmo's angry because Jay-Jay got the cops when Elmo attempted to mug an old woman (Mrs. Miller) who leaves food on the park bench for Jay-Jay, and Jay-Jay's mad because Elmo once took Jay-Jay's only souvenir of his mother -- a medallion. As in all fairy tales, the dragon gets slain in the midst of his evildoings, and the hero emerges from the wilderness to return to society -- for Mrs. Miller needs companionship as much as Jay-Jay needs a mother and a warm place to sleep on cold winter nights. A small book on that favorite habitat for runaways and revenants, writ large for old and young in sentiment which often works.