Isolation, like marriage, can test one´s mettle, as Marge and Zelda discover. Recently widowed, they have more in common than the sudden loss of their husbands: courage, determination, defiance, self-esteem, a zest for living. But urban society can be coldly judgemental toward widows in mourning, and the two ladies welcome an opportunity to serve as summer wardens of remote Trowbridge lighthouse in northern Lake Superior. There, they experience freedom from prejudice and an opportunity to regain control of their destinies. Unfortunately, forces on Trowbridge Island prove to be as treacherous as the surrounding waters of Lake Superior.