Daphne du Maurier. Frenchman's Bay

On the threshold of her thirtieth birthday, the beautiful Donna St. Columb becomes acutely aware of the emptiness and futility of high society life and, on impulse, leaves London for the secluded castle of Navron on the coast of Cornwall. There, she meets an elusive pirate leader, known simply as the Frenchman, and with him, love and, albeit short-lived, happiness.