It then proceeds to a dramatization largely following the exploits of main character William Foster (Crispin Glover) during the attempt to cross the Sierra Nevada mountains and his group that would be later known as "The Forlorn Hope" whilst seeking rescue for the broader Donner Party (the film chooses to focus on a select few characters, while in the real-life background the Donner-Reed Party considered of a fairly large group of multiple families).

The film takes several artistic liberties with the true story basis, and combines multiple real-life historic figures from the Donner-Reed Party into these characters.

Foster finds himself consistently at odds with fellow pioneer William Eddy (Clayne Crawford), and the group begins to bicker as rations grow more scarce.

Eddy later has disturbing delusions in his sleep of his wife, Eleanor (Jamie Anne Allman) standing in the snow in a white dress, totally emaciated, holding a deceased infant's corpse as it drips with blood.

Foster finds Luis and bludgeons him to death before eviscerating his corpse off-screen; meanwhile Eddy collapses in the snow from illness due to starvation, and his wife sneaks him meat.

As the group continues to starve and freeze to death, Foster is left weak and shivering under blankets, and to his surprise, Eddy acts as an ally and offers to go seek rescue with the aid of fellow pioneer Mary Graves (Alison Haislip).

Eddy and Mary rip open Jay's abdomen, remove his intestines and liver, and begin eating these internal organs while a horrified Ann flees.

She comes upon a freezing Foster, who comforts her and is revealed to have been the more trustworthy and sane of the group after all, in comparison with Eddy, who decides to continue alone on the journey to California, leaving Mary behind to die.

The film ends with William Eddy collapsing in the snow, presumably near his destination as two men are shown discovering his fallen body, the sound of his heart still beating as he is finally rescued.

The camera slowly pans out, with captioning on the screen indicating that Eddy's wife and son (who remained behind in Illinois) had died sometime over the winter; of the "Forlorn Hope" group, only 5 survived.