James was adopted by loving parents fifteen years ago, but just lately he has begun to wonder about his birth mother. Had she wanted him, and why had she left the ammonite - the snake-stone - with him when she abandoned him? He becomes difficult at home and his relationship with his father, who is training him for the Junior Diving Championship, deteriorates. He finds some clues that lead him to the village he believes he came from, and he runs away in the belief he will find his birth mother. The fact that he does helps him to grow up and leads him back to his real home and adoptive parents. Interspersed with James' adventures and worries are sections containing his birth mother's memories of her brief liaison with the 'wild boy', James' birth, and her brave trek to take him where she believes he will be safe. It is a moving story, and while James is fifteen and there is an incipient love interest between him and a girl he meets along the way, there is nothing here that mature under 12's could not handle. Beautifully written.