In the midst of Nazi air raids, a postman dies on the operating table at a rural hospital. But was the death accidental?

A shiftless dreamer, Michael Rogers (Hywel Bennett) fantasizes about a lifestyle above his means and marries a wealthy, young girl, Ellie Thomsen (Hayley Mills) who just came of age. They hire a famous architect to build their dream home amidst a series of suspicious incidents. The spouse has dark intentions toward his naive, inexperienced bride. Secrets from his past and sinister ties to their houseguest Greta (Britt Ekland), lead to a terrible turn of unexpected events.