In 1914 the 28 member crew of the Endurance left to trek across the continent of Antarctica on foot. It is now the beginning of 1916. Their ship has been crushed, they've been stranded on the ice with no way out, and they've taken to the boats in a last ditch effort to escape the ice melting beneath them. In Part 4 we hear what happens next as they head for the yet unexplored Elephant Island, and Shackleton with a sets out on an 820 mile open boat journey on the roughest sea passage in the world to either find rescue, or doom them all to an icy grave.