Under Still Waters (2008)

Frustrated mediocre architect Andrew takes his wife, tycoon Conrad's daughter Charlotte 'Charlie', for whom he left his New York career, to her family's isolation country lakeside cabin for the weekend. On the way, they nearly run over ex-con drifter Jacob and take him along. During a boat trip, the gun he's found to have in his backpack gets accidentally fired and lost. In the cabin, tensions and hidden agendas become obvious, leading to a tragic climax.