A strange illness begins to show itself while another more familiar one jeopardizes the expedition's most valuable resource - its captain's judgment.
The weather outside the ships continue to worsen with severe storms and temperatures reaching minus fifty two. On board Erebus, Goodsir speaks with Lady Silence in an effort to learn her language but has little success learning about the nature of the creature. Crozier becomes temperamental as his liquor supplies run out and sends Lieutenant Edward Little to pilfer bottles of whiskey from the private stores of Commander James Fitzjames aboard Erebus.
Crozier calls for Goodsir and with his help along with Thomas Blanky, attempt to interrogate Lady Silence. They learn the creature is called "Tuunbaq" and Blanky believes it might be supernatural in origin. When pressed on how to kill the creature she refuses to cooperate causing Crozier to threaten her and she taunts him about his inability to do anything and his lack of a will to live. The interrogation is interrupted by Fitzjames who's come to confront Crozier regarding the stolen whiskey to which Crozier physically attacks Fitzjames causing him to be restrained.
An angered Crozier sends Blanky outside to get a report on the ice but he is soon attacked by the Tuunbaq, which is revealed as a polar bear-like creature with vaguely human facial features. It pursues Blanky up one of the ship's masts, mauling his leg so severely that it later requires amputation. The men manage to wound the creature with a cannon causing it to flee and Lady Silence escapes during the commotion. Goodsir searches her room and discovers pieces of lead she found in the canned foods. Crozier resolves to go sober delegating command of both ships to Fitzjames while he suffers through alcohol withdrawal.
- In the original script; the Tuunbaq was to destroy HMS Terror in process of attacking Thomas Blanky (similarly to the fate of HMS Erebus in the novel). This change (between the original script and what was actually filmed) was due to the fact that the wreck of Erebus was found on September 2nd, 2014 and the show had not yet begun filming when the nearly intact Terror was discovered on September 12th, 2016. Thus, the script was changed to match with the historical findings of Terror and Erebus.