As part of the 1845 Franklin Expedition to to navigate the Northwest Passage, the men aboard HMS Terror are as scientifically supported an enterprise as has ever set forth. As they enter a second summer in the Arctic Circle without a thaw, though, they are stranded in a nightmarish landscape of encroaching ice and darkness. Endlessly cold, with diminishing rations, 126 men fight to survive with poisonous food, a dwindling supply of coal, and ships buckling in the grip of crushing ice.
But their real enemy is far more terrifying. There is something unknown out there in the frigid darkness, constantly clawing to get in.
When Sir John Franklin meets a terrible death, Captain Francis Crozier takes command and leads his surviving crewmen on a last, desperate attempt to flee south across the ice. But as another winter approaches, as scurvy and starvation grow more terrible, and as the terror on the ice stalks them southward, Crozier and his men begin to fear that there is no escape.