In 1914 Sir Ernest Shackleton leads twenty-seven men on the Imperial Trans-Antarctic Expedition. The expedition intends to transverse the Antarctic continent by dog sledge. In December, 1914, the expedition, aboard the purpose-built polar exploration ship Endurance, enters the pack ice of the Weddell Sea off the coast of Antarctica some 1,100 nautical miles east of the Palmer Peninsula. By January, 1915, Endurance is a scant 60 nautical miles from its intended landfall—but it is also frozen immobile in pack ice that extends to all horizons. Endurance drifts with the pack ice for several months, eventually losing sight of land as the typical Weddell Sea current spins the vast pack ice floe in a slow clockwise direction.

As the pack ice transcribes its giant clockwise rotation, so ends the Antarctic summer. By late October, 1915, Endurance drifts some 500 nautical miles to the north-east, frozen fast in apparently limitless pack ice. In the intervening months the crew leads a generally optimistic life of boredom and intense cold even as the gradual realization sets that the trans-Antarctic nature of the expedition has failed. As the weather turns ever colder, the pack ice thickens and winter storms drive the floes together with increasing pressure and violence. At the end of October, 1915, the Endurance finally succumbs to the intense pressure and is slowly crushed. The crew, led by Shackleton, abandons ship and makes camp on a huge floe of pack ice. They salvage as much food and material as possible, and the expedition's dogs, sledges, and boats, are stockpiled on the floe. The crew establishes a makeshift home and names the drifting place Ocean Camp. Over the next few weeks the crew continues salvage operations as Endurance is slowly but entirely crushed. In late November, 1915, Endurance finally slips entirely beneath the sea; meanwhile the initial floe has crumbled under pressure and the crew has relocated to a larger, sturdier floe and established Patience Camp.

A few abortive attempts are made to sledge over the pack ice but slushy conditions and endless pressure ridges make it obvious that any sledging attempts are doomed to failure. After several days of work, only a few miles are covered in the sledges—less distance, in fact, than the floe has drifted with the Antarctic current during the same time period. The hapless crew remains essentially optimistic and spends the dark polar winter huddled in tents, subsisting off canned rations supplemented with meat from occasional penguins and seals. From time to time dogs are killed to conserve food and various interesting natural wonders are witnessed.

In March, 1916, the pack ice begins to break up as it finally drifts far enough north of the Palmer Peninsula that ocean currents and winds drive the mass on an erratic course. Warming temperatures bring additional game animals—but also cause the various floes to thin and begin to crumble away. The situation is indeed desperate and the ice floe upon which the men are encamped dwindles away by erosion and melting. Finally, in early April, 1918, Shackleton orders the men into the three small boats as navigable leads open in the pack ice. After several miserable days of freezing water and incredibly dangerous situations, the small craft are separated into two groups. Their planned destination is changed several times as storms or pack ice cut off various escapes; they finally, incredibly, and happily reunite just off the shore of Elephant Island where a barely tenable beach is located and land. A tiny hut is constructed, penguins and seals are hunted, their meat stockpiled, and the men prepare for a long and isolated stay.

Shackleton selects the best boat and causes all the best equipment to be placed in it. Then, with five other men, he sets sail in late April, 1918, in what is perhaps the most dangerous sea on the planet in a twenty-two foot open boat rigged with extemporized sails. For many days the battered and weary crew fights gales and traverses several hundred nautical miles to finally make landfall on South Georgia island—the closest practical outpost of civilization. However, they land on the far-side of the island which is bisected by treacherous mountains. Fearing that the small boat is now too unseaworthy to round the island, Shackleton and the two strongest men set out to cross the island—a feat never before accomplished. In a few days of incredible mountaineering and blind luck they manage to gain the far shore, locate the tiny whaling outpost, and secure their own survival. The men on the other side of South Georgia Island are quickly rescued.

Shackleton then embarks on a series of abortive rescue attempts to reach Elephant Island and retrieve the remainder of his crew. Various attempts fail due to weather, ice, or deteriorated ship condition. At the end of August, 1916, however, Shackleton and his rescue party finally reach the much-depressed survivors and take them from the forbidding shores of their temporary home. Incredibly, the ill-fated voyage did not lose a single man.