The Orphans of Salt Winds by Elizabeth Brooks

Virginia was adopted as a young girl by a quiet couple and goes to live with them in a remote manor house on the outskirts of a huge marsh. It is a solitary upbringing since the only neighbors were the well-off Deering family and both her parents weren't too keen on Mr. Deering and his loud demanding ways. Virginia just didn't like nor trust him. When a German plane crashes in the marsh, Virginia's dad goes to save him never to return. In his place, a secretly forbidden visitor joins Virginia and her mother at Salt Winds. This creates as many problems as it does joy. Told in alternating time periods by Virginia, this classic Gothic tale is as dark and mysterious as the landscape of the marsh.