Sarah, strapped to a table, freaks out that Alan's found out about the tumor; he reassures her, and an X-ray scan begins -- except Sarah's hallucinating again, including visions of vectors killing Alan and dragging him away.
That may be what Jules wishes would become of Hatake, who's telling her that he and her mother loved each other, but "when she found out about the Inuit children," she took Jules, and forbid Hatake from seeing her. Jules is disgusted by Hatake's kidnapping of the kids, doesn't buy his remorse, and thinks the stalker book is creepy. Hatake wastes an opportunity to demonstrate good faith by lying that their silver eyes are "a rare genetic anomaly." He's trying to protect her; that's not his job, she tells him, and stalks out.
Sarah's tumor has spread. Sarah has a sad about doing one last thing "that mattered" in the field, and Alan hugs her; he's glad she's there.
Anana stitches Balleseros up along with some more "soon, we will make out" sniping. Aerov comes in to report the rest of the village is fine, and to thank Balleseros for saving their bacon. He fails to glare, and it's rather disconcerting. Balleseros warns them that Ilaria Corp. "won't stop, ever," and their only chance to survive is to scatter. Anana balks.
Jules brings Alan up to speed on how Ha-stalk-e is actually her pops. Alan grouses that Hatake's done nothing but lie to them, and wonders if Hatake did "something" to Jules down on Level R. Jules is incredulous, but Alan heads off to confront Hatake...
...and comes upon him discovering security-camera footage of Dr. Adrian making off with the Narvik strains. Alan's more interested in pointing out that Hatake's being a weirdo, but Hatake says they can talk about that when other scientists aren't stealing key materials. Alan stares at Adrian on the monitor and asks where he's going. Hatake grunts that the ice will take him.
Alan looks at a map of the region and predicts that soon millions will have come down with the virus. They have to stop Adrian, and when Jules spots a deep-space listening station 50 miles away, she and Alan head for it in a Snowcat, over Hatake's strenuous objections. In the cab, Jules asks what happened to her National Science Award. Then she asks why Alan gave Peter his ticket that night. "Is this about me and Sarah?" It's really about Jules thinking Hatake influenced the Award committee, but of course she and Alan have to have an awkward fight.
Back at the base, Peter Spidermans into Hatake's office and rifles through some paperwork, and Sarah stares at a morphine bottle before heading back to the lab to run tests and have a huge headache. Hatake suggests she rest, but she'd rather spend her remaining time in the lab, even though she's about to drop a trayful of petri dishes. He asks where Alan and Jules went, admitting they didn't trust him enough to say, and sighs that he's done awful things in the name of science. Sarah kindly reminds him that Edward Jenner injected a child with smallpox in order to pioneer modern vaccines.
Alan and Jules find Adrian at the old station, lit up on vodka and negotiating with Ilaria by radio. He waves an ice axe, but Alan grabs at the bag when Adrian looks away for a second. Alan and Adrian brawl. The fight ends with Adrian tied to a chair and snarking on the "subzero" temps between Alan and Jules as Jules tries to repair the radio.
Anana tries to talk Aerov into going with them, but he's determined to slow the Ilaria troops down. Then they realize there's one Ilaria guard unaccounted for, and if he reported back, they're screwed. Aerov refuses Balleseros's help in tracking the guy down, and tells him to get everyone else out ASAP.
Sarah can't figure out what to look for in the DNA. Hatake kisses up to her about how devoted she is to science and then grabs her shoulders: "Do not give up now." Sarah's like, okay, jeez.
With Adrian leching on about Sarah and Alan impatiently looming over her, Jules gets the power going. The station lights up with Christmas decorations and a creepily slow recording of carols -- but a sniper's laser dot appears moments after her mayday call, and an Ilaria rep outside orders them to throw the virus outside and nobody will get hurt. With Adrian slumped dead in his chair, the radio comes alive with a German-language response. Alan tries to reach the mic, and the sniper shoots it.
Hatake finds Peter in his office, looking at the Jules stalker album. Hatake says he's there to help and it'll all be over soon. "Sooner. Than. You. Think," Peter overacts, and Spidermans up into the ceiling again.
Alan chooses now to admit that he was close to a breakthrough the night of the award thingie. They argue about it some more while shots ping off the station; Alan confesses to smashing the award after Jules left, she says she lied about the last time she saw Peter, and everyone's apologetic. Alan notices a trapdoor under Adrian's chair.
Sarah video-logs her re-scan of Jules's DNA. Long story short, Jules's spinal fluid could kill off Sarah's tumor, so it's basically super-stem cells. Probably.
Alan and Jules stumble through the passageway below the station, where they hear singing. A guy in chains is humming "The First Noel," and he gazes at them with his silver eyes and asks them to free him. Alan gives him water and asks who he is, a question Chains dodges in favor of lunging at Jules or talking about the music. He does recognize Sutton's name, and says she made him pick a side, and Hatake stashed him down there, and he babbles on about rules, "there can be no more than 500," eternal life is a mixed blessing, on and on. Bottom line: Ilaria (which is an extinct species of marsupial, by the way) is engineering an immortal super-race.
Anana still doesn't want to leave. Balleseros is ashamed of his past misdeeds. They kiss, finally.
Alan doesn't buy Chains's story; Jules thinks there's something to it after what she's gone through, so when Alan goes to find a hiding spot for the Narvik, Jules creeps over to Chains with a pair of bolt-cutters. As Sarah gets hit with another seizure back at the lab, Chains reveals he's been down there 29 years, dreaming of his revenge on Hatake. Why does Jules hate him? Before she can answer, Alan says they have to go. Chains asks again, "Free me," and Jules is about to, but then he grabs her, forcing her to close the cutters on his neck. It turns out that's the freeing he means. "Nothing can fill an eternity," he warns her about her future, and she cuts his carotid, shrieking. He bleeds horribly, but looks content.
Then the Ilaria sniper appears. His plan is to beat on Alan (or threaten Jules) until he gives up the virus, but he's shot in the back by Aerov, allowing them to throw the virus cooler into a fire. That seems like a great way to spread the virus, but everyone's apparently cool with it, and Aerov gives the Snowcat a jump.
Alan returns to the base to find Sarah in a medically-induced coma after numerous seizures, and Hatake says she doesn't have long. Hatake may not have long; Jules is furious about Chains, though Hatake says he betrayed Jules's mother to Sutton: "It was a death sentence." Jules guesses, and Hatake confirms, that 500 immortals run Ilaria. Before we can find out more, Sarah codes, and Jules, Alan, and Hatake fight to save her as we hear Sarah in voice-over, saying she's not scared and she'll leave a legacy thanks to the conservation of matter, or something.
Alan cries as he watches Sarah's vlog; Hatake comes in to say she doesn't have much time, but Jules can save her.
In an AC duct, Peter tapes pictures of Jules to the sides and looks sad, while Jules sneaks a peek at the Narvik she actually didn't destroy back at the station. Dun!