Deliberate mistake: Frank Beardsley moves his family into an old, defunct lighthouse, and subsequently makes a project of restoring the rotating lamp and actually running it. But lighthouses are navigational devices. Each one in use has its own unique, catalogued period, which identifies it and therefore helps a distant ship determine its own position. By running a "phantom" lighthouse, Frank, a career Coast Guard officer, risks confusing ships' navigators at sea. No real nautical officer would do such a thing.