In August 1914, days before the outbreak of the First World War, the renowned explorer Ernest Shackleton and a crew of twenty-seven set sail for the South Atlantic in pursuit of the last unclaimed prize in the history of exploration: the first crossing on foot of the Antarctic continent. Weaving a treacherous path through the freezing Weddell Sea, they had come within eighty-five miles of their destination when their ship, Endurance, was trapped fast in the ice pack.