Someone drags (a somehow still alive) Balleseros from where he fell as Alan eulogizes Doreen -- then bellows at Aerov that he wants Balleseros found.
Sarah wheels Dr. Van Eigem's body down a hallway and comes upon Alan and Aerov. She admits that she mercy-killed Van Eigem with morphine. Aerov makes a sarcastic remark, and when Alan announces that he's going to Level R to retrieve Jules, Aerov unholsters his pistol and says that isn't happening. They yell at each other for a few minutes; Alan stomps off.
Jules is visibly sicker; wandering down a hall, she comes upon a little girl cradling a dolly. It's probably herself as a child. The girl runs off, and when Jules follows, a hallucination of Peter sneaks up behind her. Realizing he's not real, Jules tells him to go away, but he stays, and they come upon the little girl again. This time the girl has the black-bloody mouth of a vector, and she attacks Jules... who wakes up. Hatake is passed out on the exam table nearby. A man is dying horribly outside. Jules cowers.
Alan's determined to get to Level R, as Jules literally wrote the book on infectious diseases and is their only hope. Sarah isn't enthusiastic: they don't know if Jules is still well enough to work (read: "she could be dead by now"), and they have no practicable way to get to Level R in the first place. Alan says they'll have to improvise. He's also found a non-narcotic medication for Sarah's migraines. Sarah stares at him puppyishly.
Jules happens past a mirror and is horrorstruck at her own appearance. She's even more stricken by Hatake's wound, which is healing really quickly. She angrily asks why Hatake let her keep hallucinating "Jaye" Hatake says gently that speaking with Jaye seemed to help Jules, so he didn't see the harm. The Hippocratic oath isn't much in evidence moments later when a woman pounds on the door begging for help. Hatake grabs Jules, saying not everyone can be saved, but she shoves him away and goes to the door -- then falls into Hatake's arms, having a seizure.
Alan MacGyvers a chemical metal-cutting solution that cuts through a grate. He and Sarah head through the vent system (we assume) and come upon a padlocked door. Alan grumbles that this isn't quarantine, it's locking up the sick and forgetting them. As he's sawing through the chain, a vector smashes the glass and claws at Sarah and other vectors rush towards the sound. Alan has to saw the vector's arm off to get Sarah free.
Post-escape, Alan reiterates that he can't lose Sarah. There's an awkward pause that almost gets romantic before he observes that, if they can't get to Jules -- and treat the other vectors -- "they'll bury this base, with us in it."
Jules comes to to find Hatake shining a light in her eyes. He speaks soothingly -- or so he thinks; it's actually creepy -- and injects her with something so she'll sleep, which she doesn't want to do. After Jules passes out again, Hatake blocks her exit with a big cabinet, then slips out through a secret door behind a bookcase.
Balleseros wakes up as well; he's in someone's suburban-looking house, cuffed to a coffee table, his wound wrapped in seaweed. A woman named Anana explains that she's local law enforcement, the only one in 400 miles, and proves her bona fides by kicking away the scissors he's reaching for and throttling him into submission. She adds that if he doesn't talk to her about Arctic Biosystems, she'll bring him back to the base and let whoever tried to kill him finish the job.
Alan calls Sarah to the microscope: the virus isn't just invading other cells, it's delivering something into them. Spotting Hatake and Aerov watching, Alan charges into Hatake's lair: What's in the virus? What's the endgame? Hatake denies everything, but Alan grabs him by the collar and says Hatake used his brother and ex-wife as lab rats. Hatake finally admits that the virus delivers a cancer cure. Sarah accepts this immediately and breathes that it's "brilliant" -- way to subject it to scientific study, Doctor -- but Alan says the virus changed Peter's personality, so what else did Hatake add to the Narvik B strain? Hatake says they hadn't put the gene therapy into that strain yet. Something's in it, and Alan's going to find it.
Now Aerov demands to know what's really up with the virus; he can't protect Hatake if he doesn't know what's going on. Hatake won't say, and bitch-slaps Aerov when he reveals he ice-axed Balleseros for finding Dr. Hvit. When Balleseros doesn't check in, Hatake worries, "they will come."
Anana offers Balleseros food in exchange for info about the base research. "What about the children?" Balleseros doesn't know about any children, so he doesn't get to eat.
When Jules wakes again, she's in a cozy lodge, by the fireplace, with the little girl and Peter. Hallucipeter suggests that Julia Jr. is trying to get Jules to remember something. Jules asks Julia Jr., and realizes she's in her childhood home in Montana.
Lab montage! Alan and Sarah pipette virus extract and grape Kool-Aid into petri dishes. Moments later, black arm-like things pop out and begin crossing the table. Alan freezes them with liquid nitrogen, and he and Sarah realize they can put vectors "on ice" to slow the disease.
They tuck icepacks all around Peter, and Sarah keeps freaking out about the black virus arms. Alan tells her to prep Peter to move to Level G, where there's a cryogenics lab.
Balleseros grabs Anana by the neck and demands the cuff key, but she pulls a gun and frog-marches him over to a collage of missing kids who disappeared within 200 miles of the base. She thinks Arctic Biosystems is to blame.
Alan finds Dr. Adrian, the cryo expert, drinking vodka and watching the Three Stooges. In exchange for his help, Adrian wants Alan to get rid of the guards and put him first in line to leave the base; Alan's like, fine, fine, I need to deep-freeze my bro -- does cryotherapy work? Adrian's lab rats indicate that it does.
Balleseros lock-picks the cuffs with a pen, grabs a knife, and peeks out the window to see Anana giving a huge hug to -- Aerov. Dun! Balleseros launches himself at Aerov and puts a knife to his throat, but gets Anana's gun to his head, again. Balleseros orders her to ask Aerov about the base, but Anana thinks he's nuts: "That's my brother, Tulok!" Huh?
You guessed it: once Balleseros is back inside (and cuffed), Anana reveals that her brother's twin, "Miksa," vanished when they were kids. Balleseros won't tell her anything, just that he needs to get back to the base. "We need to get back to the base," Anana grits.
Adrian explains that Peter will be suspended in the cooling solution and breathing it into his lungs, in a way. As the cooling begins, Jules hallucinates a Thanksgiving dinner at which Alan and Peter blame each other for ending up in her virus-addled head, Sarah snarks that Jules isn't asking the right questions, and Hatake asks for the cranberry sauce. When Jules carves the turkey, black blood runs out, and everyone laughs.
Despite a rocky transition, the cryofluid seems to work on Peter, but outside, Hatake glares, and Aerov apologizes for disappointing him: "Please forgive me, Father." So that's how it is. Hatake passive-aggressively blames himself for not preparing Aerov properly, but Aerov can make it up to him by producing Balleseros's corpse.
Sarah comes in to report that Peter's brain activity is improving, and finds Alan crying. They kiss. Then they get busy. Outside, Aerov returns to where he axed Balleseros, but his body is gone. They'll have to deal with it later, Hatake says as two helicopters sweep overhead: "They're here."
A postcoital Alan and Sarah stare awkwardly into the middle distance. The PA announces the arrival of the choppers, and Alan doesn't know how they knew to come: "I never got the call out." On the helipad, the Ilaria Corporation choppers land; Hatake looks ill. And Jules wakes up screaming, with silver eyes.