In October 1863, Ian Steele, having taken on the identity of Captain Samuel Forbes, is fighting the Pashtun on the north-west frontier in India. Half a world away, the real Samuel Forbes is a lieutenant in the 3rd New York Volunteers and is facing the Confederates at the Battle of Mission Ridge in Tennessee. Neither is aware their lives will change beyond recognition in the year to come. In London, Ella, the love of Ian's life, is unhappily married...