Emily Taylor, a young headmistress from Yorkshire, first sails aboard the RMS 'Lusitania' in 1910 whilst travelling to attend a family wedding on Long Island in America. During that first voyage, she makes a number of acquaintances, all with secrets in their pasts: Amelia Davenport, a flamboyant elderly widow with a salacious history, who is emigrating to America with her son and his family; Sam Jackson, a tough New York Police Inspector, driven by a personal vendetta; Christian Verholt, the heir to a wealthy banking dynasty whose double life includes a mysterious partner; and Niall Branigan, the charming Irish doctor whose twinkling emerald eyes mask hidden family secrets. But as the threat of the First World War looms, it is not only Emily's life that changes dramatically as a consequence of these encounters, but also the lives of those close to her back in England.

Emily Taylor had not expected to find romance on board the RMS 'Lusitania'. Whilst travelling to attend a family wedding on Long Island in 1910, the young headmistress makes a number of acquaintances, all with secrets in their pasts. Encouraged by the flamboyant, elderly widow, Amelia Davenport, Emily becomes mutually attracted to the handsome Irish doctor, Niall Branigan. Returning to England, the couple marry in secret, so that Emily can retain her position as a headmistress.

As the threat of the First World War looms, Emily travels to Paris to locate her wayward sister, Olivia, who is on the edge of being drawn into a dangerous life of crime. Her employer, Christian Verholt, the heir to a wealthy banking dynasty leads a dubious double life involving a mysterious partner; both are being investigated by a tough New York Police Inspector, Sam Jackson, a man who is driven by a personal vendetta. His investigations lead him to Ireland where he discovers that Niall Branigan's family have a disturbing past. The disclosure of his findings to Emily poses many questions about the family of a husband who has gone missing in war-torn Europe.

An unlikely mutual affection gradually develops between Emily and the hard-bitten Police Inspector, a man with scores to settle and whose crusty nature belies a faint remnant of tenderness. But the strength of their relationship is finally put to the ultimate test when the Lusitania, the ship they are both travelling on, is torpedoed in May 1915. The impact of this disaster has far reaching consequences for all, especially Emily and her missing husband.