At the height of a stifling summer, Jessica Leigh, a smart, tough, Westminster lobbyist, arranges a holiday at Fallings, the beautiful country home of the late Sir Lewis Appleby, a pioneering geneticist. Her lover, Stephen, is hosting a conference there and to her displeasure they are joined by his journalist brother Alex.
Jessica discovers with Alex an exquisite, ruined shell house in the grounds, which Sir Lewis had been building for his wife, Katherine. But Katherine vanished before it was completed and Jessica resolves to discover why.