When a mysterious deadly plague descends on the earth, David Kerans, his wife Felicia, their friend Lanyan, and Lanyan’s girlfriend Natalie take refuge in a campground a few thousand feet above Boulder. They locate a cabin and plan to hunker down for the duration of the winter, subsisting off of canned goods. But then Felicia takes a nasty fall while gathering firewood and breaks her knee at the shin—a compound fracture that the group is ill-equipped to treat. Lanyan splints the bone to the best of his ability, but David insists that they take her back to Boulder for medical treatment. Lanyan and Natalie are reluctant, and the three have a tense standoff. The next morning, Lanyan relents, and they drive down the campground as temperatures fall and a violent snowstorm begins. Unable to drive on, the friends occupy an abandoned house for the night. David begins dosing Felicia with oxycodone and other drugs, and the group attempts to get news from the television, the radio—but only hear static. As Felicia’s condition worsens, Natalie is pretty sure she hears something predatory outside in the wind, “metallic screeches.” Natalie speculates that aliens are fumigating the earth of human vermin to prepare for colonization of the planet. And it turns out that Natalie is right, when mere hours later the lifeforms penetrate the house and attack. David has a choice: he can either die with Felicia, or flee with Lanyan and Natalie. He stabs Felicia with the hunting knife and runs outside.