A beautiful temptress re-kindles an old romance while trying to escape her past during a tension-packed train journey.

A cavalcade of English life from New Year's Eve 1899 until 1933 seen through the eyes of well-to-do Londoners Jane and Robert Marryot. Amongst events touching their family are the Boer War, the death of Queen Victoria, the sinking of the Titanic and the Great War.

A writer named Adrian Messenger believes a series of apparently unrelated "accidental" deaths are actually linked murders. He asks his friend Anthony Gethryn, recently retired from MI5, to help clear up the mystery. However, Messenger's plane is bombed while he is en route to collect evidence to confirm his suspicions and, with his dying breath, he tries to tell a fellow passenger the key to the mystery.