This piece contains spoilers for The Last of Us finale. If you haven’t watched yet then check out our spoiler-free season review here.
In the post-apocalyptic world of The Last of Us, the hope of Ellie’s immunity has always been at the center of the story. But, while the game never explicitly revealed how the girl became immune to the Cordyceps virus, the heartbreaking finale of the HBO series offers up an answer that seems to confirm one of the most popular The Last of Us fan theories.
What Happens to Ellie’s Mom in HBO’s The Last of Us Finale?
In the opening moments of the finale we meet Ellie’s mother, Anna (Ashley Johnson). She’s running through the woods, heavily pregnant heading for an empty safehouse. It’s a brutal journey and Johnson — who played Ellie in the original games — sells every second. Sadly for Anna, the friends she’s expecting to meet at the safe house are nowhere to be found, leaving her to give birth alone. Before she can welcome baby Ellie into the world, she’s attacked by a virulently infected woman. Using her knife — that viewers will recognize as the one Ellie carries now — Anna kills the monster, but not before getting bitten. Moments later Ellie is born, still connected to her mother by umbilical cord, meaning the infection is in Ellie’s blood already.
Did Ellie’s Mom Get Bitten in the Game?
No. That’s why this is such a huge moment. In the games, fans never knew how Anna died or whether she was infected. In the 10 years since its release, The Last of Us die-hards have often pondered whether Anna may have been infected thanks to Ellie’s immunity and a letter that gamers can discover in Ellie’s things. The emotional screed was written by Anna before she died and includes this line that sparked 1000 fan theories: “You’re not even a day old and holding you is the most incredible thing I’ve done in my life — a life that is about to get cut a little short.” While some fans argued that Anna probably died of natural causes, many theorized that Anna was infected and Ellie being born with the infection acted as an inoculation, giving the young girl her immunity. And the finale of the show goes a long way to confirm this.
Why Did Marlene Let Ellie Live?
In the context of the episode it’s clear that, just like in the game, Anna and Marlene are friends. As Anna sits with Ellie, a knife to her neck as the infection spreads, we see Marlene arrive and realize that Anna — and likely her child — are infected. But Anna promises her that she cut the cord before she was bitten. It’s clear that Marlene doesn’t quite believe her, but she chooses to let Ellie live after shooting Anna in the head (at her request). While it’s clear that Marlene saves her friend’s baby out of love, Ellie also becomes extremely valuable. And when Joel and Marlene reunite at the hospital it becomes clear that her knowledge of Ellie’s past and infection at birth have shaped the plan to use her to create a vaccine.
This is a massive swing from the game too, as there Marlene’s only interest in Ellie is her connection to her mother. But, here we see that she’s been keeping her safe and watching over her because she suspected — correctly —that Ellie might be immune.
How the Show Changes the Truth About Ellie’s Immunity.
In the game — just like the show — Marlene is the one who tells Joel about Ellie going into the surgery which will kill her but potentially save the rest of the world. But, in the game her reasoning for why Ellie is immune is far more vague. “The doctors tell me that the Cordyceps, the growth inside her, has somehow mutated. That’s why she’s immune.”
However, in line with the reveal that Ellie’s mother was bitten and that’s how Ellie gained her immunity, the show changes and expands on this vital moment. Instead, Marlene tells Joel that “our doctor, he thinks that the Cordyceps in Ellie has grown with her since birth. It produces a kind of chemical messenger, it makes normal Cordyceps think that she’s Cordyceps. That’s why she’s immune.” As Marlene pleads her case to Joel we get another big confirmation. If the doctor knows Ellie has been infected since birth, then it means that Marlene shared that knowledge with him. It’s more concrete proof that Marlene’s keen interest in Ellie throughout her life was more to do with her potential immunity than any connection to Anna.
What Does This Change Mean For Season 2?
This is arguably the most interesting question surrounding the reveal of Anna’s infection being the cause of Ellie’s immunity. While there are plenty of burning moral quandaries to break down, the truth about Ellie has big ramifications. If she gained her immunity via her mother being bitten, then surely there are other children who could be immune.
A bleaker option also appears out of this reveal: If the wrong person or organization finds out the truth about Ellie’s immunity, then what if they start trying to replicate it by infecting pregnant people with the virus? Though Joel seemingly killed the only living humans who knew the truth, that doesn’t mean that there’s not others who could exploit the information. It’s a scary thought and one that could massively impact the story going forward.
In adapting its most shockingly brutal chapter and bringing a fan favorite theory to life, the series has expanded what we know of both the Cordyceps and Ellie’s history. But, as we laid out, it also introduces a possible massive diversion from the game in Season 2.
