On May 19, 1845, Sir John Franklin and the 128 men under his command set forth from Greenhithe, just east of London on the River Thames, to find the long-sought Northwest Passage believed to link the North Atlantic and the Pacific oceans. But after getting trapped in the ice, Franklin's men were stalked and killed by a gigantic monster that looks like a polar bear with an elongated neck.
That's the plot of AMC's The Terror, which takes the true story of the Franklin Expedition as the jumping off point for a survivor horror tale, complete with a mythological Inuit monster. But monster aside, The Terror has remarkable fidelity to the actual Franklin Expedition and it's equally grim fate. So what's the true story behind the loss of the HMS Erebus and the HMS Terror?
The Franklin Expedition began with remarkable promise. Franklin was already a famed explorer (his expedition journals are available online), with three previous Arctic expeditions under his belt. With Franklin (played in The Terror by Ciarán Hinds) captaining Erebus, Terror was put under the captaincy of Francis Crozier (played by Jared Harris), who had previously captained Terror on an Antarctic expedition.

The two ships, both bomb vessels designed for mortar bombardments, had been field-tested in multiple expeditions. For Franklin's search for the Northwest Passage, Erebus and Terror were outfitted with locomotive steam engines, which could enable speeds of up to 4.6 miles per hour.
The crews were well-provisioned, with 36,487 pounds of biscuit, 136,656 pounds of flour and more than 97,000 pounds of beef, pork and tinned meat. They even brought along a 2,400 volume library and a daguerreotype apparatus (though evidence suggests it was only ever used to take photos of the officers before the expedition launched).
On July 26 the crews of two whaling ships spotted Erebus and Terror in Baffin Bay, west of Greenland. It would be the last time the Franklin Expedition was seen alive.
After waiting out the winter, Franklin's ships sought the Northwest Passage by sailing down the west coast of King William Island (then known as King William Land). In AMC's The Terror, this is portrayed as the point of no return for the crew, with Crozier urging Franklin to instead explore King Williams Land's eastern shore, so that they might avoid getting trapped in the ice during the oncoming winter of 1846.

Whether that debate between the expedition's officers ever occurred is unknown, but the result remains the same. HMS Erebus and HMS Terror become trapped in the ice in September 1846. The ice does not thaw in 1847 and John Franklin dies aboard in June of that year. After spending another winter trapped in the ice, the crews of Erebus and Terror abandon their immobilized ships in April 1848 and voyage across King William Land, pulling their supplies and several small boats by sled across the ice. It's uncertain how far they got, but none survive.
Archaeological expeditions in the 1980s discovered the remains of Franklin Expedition crewmen on King William Island and found evidence of scurvy and cannibalism, including the "pot-polished" and cracked bones suggesting survival cannibalism's final stages, when bones are boiled for their marrow. But beyond the gruesome evidence of the crew's desperation, archaeologists found an unexpected impediment to the crew's progress across King William Island: lead poisoning from the unique water filtration systems designed to work with the ship's steam engines.
Despite numerous expeditions sent out to look for Franklin and the crews of Erebus and Terror, the remains of the two ships weren't found for more than 150 years. Erebus was discovered in 2014 by the Parks Canada Agency, Terror two years later by the Arctic Research Foundation. Inuit testimony gathered in the 19th century proved instrumental in narrowing down the search area and discovering the ships' final resting spots.

The Terror is far from the first piece of semi-fiction inspired by the ill-fated expedition. Previous adaptations include The Frozen Deep, a play produced by Charles Dickens (he also acted in it!), an adventure novel by Jules Verne, The Rifles by William T. Vollmann and famous paintings like the gruesome "Man Proposes, God Disposes." But The Terror is unique in dramatizing the real horror of the Franklin Expedition's fate with the storytelling conventions of monster movies and modern horror storytelling.
The next episode of The Terror, "The Ladder," airs Monday at 9 p.m. on AMC.