The year is 1931. The new and luxurious transatlantic liner Empress of Britain is on her eastward passage. Among the first-class passengers on board are two English confidence tricksters, making a discreet exit from a little awkwardness they have left behind them in the United States.

Harry Barnett, a middle-aged failure, leads a shabby existence. He is reduced to caretaking a friend's villa on the island of Rhodes and working in a bar to earn his keep. Then a guest at the villa - a young woman he had instantly warmed to - disappears on a mountain peak. Under suspicion of her murder, Harry becomes obsessed by the mystery that has changed his life and begins to trace back the movements and encounters that led to the moment where she vanished into the blue.

On a mild autumn afternoon in 1882, William Trenchard sits smoking his pipe in the garden of his comfortable family home. When the creak of the garden gate heralds the arrival of an unexpected stranger, he is puzzled but not alarmed. He cannot know the destruction this man will wreak on all he holds most dear.

On assignment in Vienna, photographer Ian Jarrett falls suddenly and desperately in love with a woman he meets by pure chance, Marian Esguard. Back in England, he separates from his wife and goes to meet Marian at an agreed rendezvous, only to hear her tell him on the telephone that she will not, after all, be coming. Then she vanishes from his life as mysteriously as she entered it. Who and where is the woman he met and fell in love with in Vienna?

Why should distinguished Edwardian Cabinet minister Edwin Straford resign at the height of his career? Why does the woman he loves so suddenly reject him? Why, 70 years later, should people go to such lengths to prevent the truth coming out?