Ann doesn’t know much about the world outside her island, and that’s just how she likes it. She is the lighthouse keeper’s daughter, and the cry of seagulls, the wild foaming sea, and the sturdy lighthouse tower are all she’s ever known. She resents the “summer people” who come to picnic on the island because they don’t know anything about the sea or her way of life. Ann’s world gets turned upside down when Betsy comes to the island to stay with her grandmother. Betsy is a timid city girl who knows much more about apartments and traffic than crabs and boats. Together, Ann and Betsy learn that the world is much bigger than they thought, and that friendship can be found in the most unlikely places.