The men on board The HMS Terror - part of the ill-fated 1845 Franklin Expedition - are entering a second summer in the Arctic Circle without a thaw, stranded in a nightmarish landscape of ice and desolation. Endlessly cold, they struggle to survive with poisonous rations and a dwindling coal supply. But their real enemy is even more terrifying. There is something out there in the frigid darkness: an unseen predator stalking their ship, a monstrous terror clawing to get in.