In August 1914, Sir Ernest Shackleton's ship Endurance set sail for the South Atlantic. The object of the expedition was to cross the Antarctic overland. In October 1915, still half a continent away from their intended base, the ship was first trapped, and then crushed, in ice. For five months, Shackleton and his men, drifting on ice packs, were castaways in one of the most savage regions of the world.
The first message sent to Tom Thorne's phone was just a picture - the blurred image of a man's face, but Thorne had seen enough dead bodies to know that the man was no longer alive. But who was he? Who sent the photograph? And why? While the technical experts attempt to trace the sender, Thorne searches the bulletins for a reported death that matches the photograph. Then another picture arrives.