A body of water

"Moss and Avis, an attractive, middle-aged couple, wake up one morning in an isolated summer house high above a picturesque body of water. The weather's fine; the view's magnificent. There's only one problem, neither of them can remember who they are. When a young woman named Wren arrives, information starts to flood in. But will it help? Her explanations seem only to make Moss and Avis' world—as well as ours—more terrifying" -- publisher.