The ice has forced Terror’s stern more than a dozen feet higher than it should be. The hull there is still locked in, but only by several hundred heaped tons of jagged sea ice and the added tons of snow the men have piled alongside to within a few feet of the railings so as to provide more insulation during the
winter. Something, Francis Crozier suspects, has dug down through these tons of
snow and tunneled through the iron-hard slabs of ice to get at the hull of the ship. Somehow the thing has sensed which parts of the interior along the hull,
such as the water-storage tanks, are lined with iron, and has found one of the
few hollow outside storage areas — the Dead Room — that leads directly into
the ship. And now it’s banging and clawing to get in.

Chapter 3