6It's lady's maid Louisa Cannon's wedding day, but the fantasy is shattered shortly after when she is approached by a secretive man asking her to spy on Diana Mitford — who is having an affair with the infamous Oswald Mosley — and her sister Unity. Soon, as summer 1933 dawns, Louisa finds herself accompanying the Mitfords on a glitzy cruise in the Mediterranean, full of the brightest stars of society. But the waters run red when a man is found attacked.