10 Things You Need to Remember About The Last of Us After the Long Wait For Season 2

Joel (Pedro Pascal) and Ellie (Bella Ramsey) look down from a rooftop in The Last of Us

HBO's The Last of Us is a post-apocalyptic drama series based on Naughty Dog's critically acclaimed video game series of the same name. Season One aired on January 15, 2023, and ran for nine episodes. Season One covers the events of the original Last of Us (2013) game from start to finish, including the Left Behind DLC (2014) that focused on Ellie and her best friend/love interest before Ellie met Joel.

The HBO series also proved to be incredibly popular, both with fans of the game and new viewers who had never played The Last of Us. Gamers praised it for being a faithful adaptation of the video game, while new fans were enchanted by the show's unique and terrifyingly realistic approach to a zombie apocalypse. Season Two will finally air on April 13, 2025, over two years after the conclusion of the first season. This list will cover some of the most important details from Season One that fans need to remember before watching Season Two.

10. The Last of Us Might Seem Like a Bog-Standard Zombie Show at First Glance

But the Cordyceps Brain Infection is So Much Worse

A Cordyceps infection chart from HBO's The Last of Us.

The Last of Us doesn't feature a typical zombie virus or a typical zombie apocalypse. In fact, the franchise isn't technically about zombies at all. The Cordyceps brain infection (CBI) is actually a parasitic fungal infection. The most terrifying part of CBI is that it's somewhat realistic because Cordyceps actually exists. Commonly referred to as the "zombie fungus," Cordyceps is a genus of parasitic fungi. In the series, a mutant strand of Cordyceps known as Ophiocordyceps is actually what causes CBI.

In the world of The Last of Us, there is no cure for the Cordyceps brain infection.
Apidemiologists Neuman and Schoenheiss put forth the theory in 1968 that CBI could be humanity's future. No one listened.
The show alters when the outbreak first happens. In the game, the outbreak happens in 2013, but in the series, it happens in 2003.

Ophiocordyceps unilateralis is also a very real fungus. It's most commonly known for the impact it has on ants. Ophiocordyceps changes the way ants behave, ultimately kills the ants, and begins growing out of the ants' bodies. As Ophiocordyceps blooms from the heads of its hosts, it produces spores. This is, more or less, what happens to humans in The Last of Us. The HBO series suggests that global warming has allowed this fungus to mutate so it could infect humans.

9. The Cordyceps Brain Infection Features Several Notable Stages

The Most Iconic of Them is the Clicker, a Monster The Last of Us Became Famous For

A clicker, covered in mushroom-like fungus, screams in The Last of Us

In The Last of Us video games, there are about half a dozen variants or stages of Cordyceps. The HBO series simplifies it a little bit to feature only four stages. To be fair on the TV show, some of the variants from the games, like the Rat King, don't show up until the second game, so it's possible that they might show up in the show as well. Season One, however, only features four stages.

The Four Stages of Infection:

Stage One: In Stage One, the Infected still look mostly human. They usually feature dilated pupils, bloodshot eyes, and veins visible through the skin, especially around the face and neck. Tendrils made of hyphae will form and protrude from the mouth. The tendrils are how Infected spread the infection through biting. Stage One Infected started to act more animalistic as the fungus takes control of them. They also lose control of their motor functions, resulting in violent jerks, heavy breathing, panting, and even screaming. Most unnervingly, the host loses all sense of self-preservation as the fungus takes over.
Stalker: Stalkers still look mostly human, but hyphae grow beneath the skin. This causes the Infected to form skin abnormalities like lumps pushing the skin upward. Fungal plates begin emerging from the skin as well. Stalkers usually feature yellow skin and eyes. Cordyceps also noticeably favors growing out of the Infected's eyes, much like Ophiocordyceps grows from the heads of infected ants.
Clicker: Clickers are the most iconic Last of Us monsters ever. Clickers have been infected for a long time. They no longer look human. The infection has grown so severe that the Infected's skull splits in half, allowing more of the fungus to grow from the brain and push out of the skull, resulting in horrifying fungal plates consuming most of the head. The Clicker's mouth is the only thing really left intact, so it can still spread the infection via a bite. The body is also covered in rough, scale-like rashes and fungal plates, especially around the neck and upper body. Clickers are completely blind, but they use echolocation to locate prey. Their form of echolocation resembles a clinking sound, which is why they're called Clickers. Clickers are incredibly fast and strong, so it's best to avoid them if possible.
Bloater: Bloaters are the worst case of infection fans see in Season One. Bloaters are an advanced stage of infection that surpasses even that of Clickers. It takes years for an infected person to become a Bloater, so there aren't that many. The host has to survive the outside world and the infection long enough to become a Bloater, so they're a rare occurrence. They're called Bloaters because the fungus has grown so much, the host's body has expanded to a size larger than any human. They are also completely covered in fungal plates, which gives them resistance to incoming attacks, even gunshots. Bloaters are slow due to their size, but they are extremely powerful. If they get close, they can kill someone with a single hit. In the games, Bloaters are also capable of throwing spore projectiles. In the series, this is a rumor that has never been verified.

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8. Most Survivors Live Inside Quarantine Zones

But Settlements Do Exist Beyond Quarantine Zone Limits

Ellie and Riley spending final moments together in HBO's The Last of Us.

After the outbreak in 2003, the U.S. military and the Federal Disaster Response Agency (FEDRA) set up numerous Quarantine Zones for survivors who were free of infection. These zones are under strict control of the military. Everyone who lives inside a Quarantine Zone has to contribute in some way, even if that means taking some of the worst jobs imaginable. Food rations are depicted as being low as well. Overall, Quarantine Zones aren't a nice place to live, but they're mostly safe.

That said, not everyone has taken well to military occupation. Some Quarantine Zones have fallen to Infected, while others have been overthrown by rebels. Not all survivors live inside Quarantine Zones either. There are plenty of small groups and settlements that extend beyond the zones, but they're often dangerous or only looking out for themselves. Ellie and Joel cross paths with several dangerous groups, some even resorting to murder and cannibalism just to survive. Not every single settlement is hostile, though. Joel's brother, Tommy, lives in a surprisingly lovely town, Jackson, Wyoming.

7. The Military Oppression Gave Rise to the Fireflies

A Revolutionary Militia Group That Wants to Restore Democracy

The Fireflies are an important group in The Last of Us universe, especially in Season One. They are a revolutionary militia group that opposes the military oppression happening in the Quarantine Zones. They are also one of the only groups still actively looking for a CBI cure. For some, the Fireflies are a symbol of hope. They want to restore the U.S. to its former glory, or at the very least, get as close as possible. They represent freedom, democracy, and fairness.

"When you're lost in the darkness, look for the light."―The Fireflies' slogan

At the same time, the Fireflies are a radical group that will resort to violence when necessary. The show emphasizes them attacking a Quarantine Zone. Yes, that can harm the military who control the area, but it can also hurt the innocent civilians living there who are just trying to survive. The Fireflies take a special interest in Ellie because they believe she might be the key to creating a CBI vaccine. Marlene, the leader of the Fireflies, hires Joel to smuggle Ellie out of the Quarantine Zone and bring her to one of their bases.

6. Ellie is Immune to the Cordyceps Brain Infection

That's What Makes Her So Valuable to the Fireflies

As mentioned, the Fireflies believe Ellie is the key to creating a CBI vaccine. The reason the group believes this to be true is because Ellie is immune. In Season 1, Episode 7 - "Left Behind," viewers see a flashback sequence of the night Ellie was bitten by an Infected. This episode is based on the Left Behind DLC from the first game. It tells the story of Ellie and her best friend and crush, Riley, sneaking out to explore an abandoned mall. The noise the teens make inevitably summons a wave of Infected.

Ellie and Riley fight to survive, but they're both inevitably bitten. They promise to "lose their minds" together and wait for the end, but that's not what happened. Riley turned, but Ellie never did. The HBO series implies that Ellie's immunity comes from the circumstances of her birth. While in labor, Anna, Ellie's mother, was attacked and bitten by an Infected. She killed the Infected with a knife that she also used to cut Ellie's umbilical cord, which exposed Ellie to the virus. Anna was also friends with Marlene, so Marlene has a personal investment in Ellie that goes beyond her immunity.

5. Joel's Daughter Died on the Night of the Outbreak

That's Why He Tries So Hard to Keep Ellie at a Distance

Before the CBI outbreak that destroyed everything, Joel had a daughter named Sarah. Joel's entire world revolves around Sarah. Both the games and the TV show make it clear that Joel and Sarah are very close, especially since Sarah's mom isn't around anymore. On the night of the outbreak, Joel tries to flee the city with Sarah and his brother, Tommy. Sarah sustains an ankle injury during the evacuation. Eventually, Joel and Sarah come across a soldier who has been ordered to kill anyone showing signs of infection.

"It was only twenty dollars, which I stole from you. I could have stolen sixty, but I put the change back because I'm an honest thief." - Sarah to Joel

Joel informs the soldiers of the situation and insists they aren't sick. The soldier is ordered to shoot them anyway. Joel tries to protect Sarah, but the gunfire ultimately kills her. The worst part about Sarah's death is that it was completely avoidable. Her death was the result of paranoia, panic, and ignorance. If she died because of CBI, that would have been one thing, but to die because a soldier shot a child? Joel never recovered from Sarah's loss. He became a smuggler and a law-breaker after her death, uncaring of what it would cost him. His trauma over Sarah's death also keeps him from forming a relationship with Ellie at the beginning of their journey.

4. Ellie is the Only Known Case of Immunity

The Franchise Hasn't Mentioned Anyone Else

As far as the main characters of The Last of Us know, Ellie is the only known case of immunity to the Cordyceps brain infection. The series has never confirmed another individual who shares Ellie's immunity. That's not to say that Ellie is the only case. There may be other individuals who are immune and don't know because they haven't been infected or are immune, do know, and have kept their mouths shut about it.

Ellie's immunity is at the center of the entire series. If Ellie wasn't immune, she would never have gone on a journey across the country with Joel. Ellie and Joel would never have nurtured a relationship. The game and TV adaptation would be an entirely different story if Ellie's immunity wasn't a key factor. That's what makes her so special.

3. Ellie's Immunity Makes Her a Valuable Asset in Curing CBI

The Fireflies Need Her to Create a Vaccine

Ellie being the only proven case of immunity is what makes her so important to the Fireflies. Marlene, Anna's friend, is willing to subject Ellie to experimentation and even death if it means getting results. It's not an easy decision for Marlene, but it's one she feels she has to make. If Ellie has to die, so the rest of humanity can thrive again, then so be it. The Fireflies view Ellie as their only real chance to save the world from Cordyceps.

"I do. I was there when she was born, Joel. I promised her mother that I would save her child. I promised. So I do understand. I'm the only one who understands. I'm sorry. I have no other choice."

―Marlene to Joel about sacrificing Ellie

The harsh reality is that the Fireflies planned to kill Ellie. CBI is a brain infection, so they needed to harvest samples from Ellie's brain to do it. Marlene and the rest of the Fireflies lure Joel and Ellie to them under false pretenses. They both think Ellie will just go through some tests and then come out of it. To obtain the samples they need, Ellie has to die. Marlene and the rest of the Fireflies never tell Ellie this, stripping her choice away from her because she doesn't have all the information. They don't inform Joel until Ellie's already being prepped for surgery.

2. Joel Kills an Entire Hospital Full of Fireflies to Save Ellie

This Will Play a Huge Role in Season 2

By the time Joel finds out the Fireflies plan to kill Ellie, Ellie has already been prepped and taken into the operating room. By this time in the story, Joel and Ellie have traveled together for months, and they've had plenty of time to grow close. Joel saved Ellie's life more than once and Ellie saved him in return. Joel comes to see Ellie as a daughter. He loves her, and he will do anything to protect her.

"I know you mean well. I know you want to protect me. You have. And when we're done, we'll go wherever you want. Tommy's... sheep ranch... the moon. I'll follow you anywhere you go. But there's no halfway with this. We finish what we started."

―Ellie insisting that she make it to the Fireflies

The information of her impending death sends Joel on a rampage through the Fireflies' hospital. He kills anyone who tries to stop him from getting to the operating room. He even kills the doctors who plan to cut Ellie's brain open. The body count Joel racks up to save Ellie is as impressive as it is terrifying, but he succeeds in saving Ellie's life. His rampage comes back to haunt him in The Last of Us Part II, which Season Two will likely be based on. This decision sets up the entire story of the second game. The Last of Us is expected to last more than two seasons, so Season Two will likely deviate from the source material somewhat or only cover part of the second game.

1. Joel Lies to Ellie About the Fireflies

Which Inevitably Leads to Tension Between Them

After Joel saves Ellie from the Fireflies, he leaves with Ellie in his arms, still unconscious from the sedatives. Ellie wakes up in a car with Joel. Confused, she questions Joel about what happened, but Joel can't bring himself to tell her the truth. Instead, he tells her that the Fireflies stopped looking for a cure after they uncovered other cases of immunity. He also tells her that the hospital was attacked by raiders and Joel was barely able to get them both out alive.

"Swear to me. Swear to me that everything you said about the Fireflies was true." - Ellie to Joel

Ellie seems unconvinced. Joel's story doesn't seem to add up, but Ellie desperately needs to believe that he's telling her the truth. She doesn't question it until they're almost back at Jackson, where she makes Joel swear he's telling the truth. Sometime between The Last of Us and The Last of Us Part II, Ellie learns the truth, which causes a huge rift between her and Joel. This will likely be a big plot point in Season Two, so it's one of the most important moments from the original season.