Two siblings have conflicting aspirations about how to spend the time on a beach. The boy wishes to profit from an infrequent opportunity to play with wet sand, as small boys do, and is disinclined to wander. The girl has an idea nagging in her head, as girls of her age do, though she can't quite say what it is: she feels it would become clearer if she explored the lighthouse but there is the little problem of her ward and how she is to get him to comply with her wishes...