Gideon Lake, a successful composer, is immediately smitten by Kate Solway, who lives below him. They begin a passionate affair, and Kate invites him to Europe so that they can be together without her husband finding out. But when Gideon witnesses all kinds of strange and terrifying events, he soon realizes that nothing in Kate's world is what it seems. Gideon must work out who, and what, Kate really is, and what she wants from him . . .