A year after her husband's death, young widow, Diana Porteous is introduced to her agent's stylish, anarchic sister, Sarah, to pep her up. They plan that Di should rediscover her talents as a thief, as well as art expert, to recover stolen paintings - and begin with Steven, the neighbour's son, who is amassing works of art including work stolen from his mother. But if Di is interested in his illicit treasures, he is equally fascinated by hers - and in the secrets still held in that house by the sea.