Fallout season 2 episode 4 sparks a big new fan theory about what's really going on in Vaults 31, 32, and 33

Full spoilers immediately follow for Fallout season 2 episode 4.

Fallout season 2 episode 4 has arrived on Prime Video – and a seemingly throwaway line of dialog has sparked a major new fan theory about the ongoing mystery surrounding Vaults 31, 32, and 33.

Titled 'The Demon in the Snow', Fallout season 2's latest chapter is full of surprises. From the long overdue arrival of an iconic Fallout monster in the Deathclaw, to that revelation about Vault 32's recently-installed overseer Steph and more besides, it's certainly an incident-packed installment.

It's a moment in the Norm-fronted storyline, though, that's set tongues wagging among viewers after season 2 episode 4's release. And, as I hinted at above, it's one that may hold the key to solving the enigma of the aforementioned underground shelters.

Around 19 minutes into the Fallout TV show's latest entry, we're reunited with Norm MacLean, who originally hails from Vault 33, and Bud's Buds. The latter group are trainee Vault-Tec managers who were cryogenically frozen in Vault 31 before The Great War, and who were reawakened by Norm after he was trapped in Vault 31 by Bud Askins – a junior Vault-Tec vice-president – in last season's finale.

After Norm deceives Bud's Buds into helping him escape Vault 31 in this season's second chapter, he's now leading them across the Wasteland under the guise that he's part of a "race of super-managers" who've been genetically engineered over the past 200 years in order to lead Vault-Tec. That way, Norm can continue to trick them into working for him as he continues to try and determine what's really going on between the three Vaults.

That takes us up to the Prime Video show's latest episode and what's suddenly got its audience all worked up. During a conversation with Ronnie McCurtry, Bud's personal assistant, Norm – and, by proxy, us – learn of a new Vault-Tec program called Future Enterprise Ventures. Or, to shorten it to its primary initials, F.E.V.

Why is that important? Those are the same initials that stand for another hugely significant thing in the Fallout universe: the Forced Evolutionary Virus.

What is the Forced Evolutionary Virus in the Fallout franchise?

I won't get into the weeds of Fallout's extensive lore but, essentially, the Forced Evolutionary Virus is an artificial contagion that was created prior to The Great War.

Developed by the NBC Division of West-Tek, a major US defence contractor and research organization, it's a biological weapon that, as its name implies, has the ability to force-change the genetic makeup of organic matter.

Indeed, the virus has been used as a superweapon by numerous antagonists throughout the Fallout franchise, including the Master, aka the leader of the Unity, who created super mutants using it. The Enclave, a recurring and clandestine villainous faction in Bethesda's videogame series, also utilized it for genocidal purposes. In case you'd forgotten, the Enclave is the faction that Siggi Wilzig defects from early on in Fallout season 1 and sets one of the show's primary plots – the one based around cold fusion technology – in motion.

Now, none of this is a guarantee that the Master, the Enclave, or super mutants will appear in the Amazon TV Original's second season. It's also possible that the Forced Evolutionary Virus and Future Enterprise Ventures just share the same primary initials.

Comment from r/Fallout

Plenty of Fallout fans don't think the latter is a coincidence, though. A quick scan of threads on Reddit pages such as r/Fallout and r/Fotv, plus a season 2 thread on the ResetEra forums, are full of comments from viewers speculating on the prospect that the two are related.

If that proves to be the case, it might solve the mystery about the experiments being conducted between Vaults 31, 32, and 33. We already know that the trio are part of an ongoing experiment whereby, every so often, one of Bud's Buds exits cryosleep to laud it over Vaults 32 and 33, and breed with the general populace to create future Vault-Tec managers.

What if there's a secondary goal that the triumvirate's dwellers must achieve – that being, the creation of the FEV to recreate said virus for nefarious reasons – though? Vault-Tec is nothing if not a sinister, omnipresent megacorporation hell-bent on ruling the planet, so I wouldn't be surprised if we eventually learn that the FEV has something to do with restarting the Forced Evolutionary Virus program to create the "super managers" that Norm mentions in this season's second episode. Let's hope we learn more soon.

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