With World War II on the horizon, a British woman risks her life to uncover the truth behind the disappearance of her twin sister Violetta Denver and her twin sister Dorabella are inseparable—until Dorabella falls in love with Dermot Tregarland. The newlyweds settle in Dermot's isolated ancestral home along the Cornish coast, and Dorabella soon has a little boy. But Violetta can't shake the terrible foreboding she's felt since her sister's marriage. When she hears that Dorabella went swimming one morning and was swept out to sea, she refuses to believe that her beloved twin is really gone, so a grief-stricken Violetta travels to the Tregarland estate. There, against the terrible grandeur of sea-swept cliffs, Violetta learns that Dermot's first wife also drowned under suspicious circumstances. When death claims another victim, Violetta knows the answer lies in the history of the Tregarlands—and a haunting legacy of madness and bad blood. With the help of Jowan Jermyn, Dermot's neighbor, Violetta moves closer to the truth . . . and closer to a murderer whose long-awaited revenge is about to come full circle.