11 details you may have missed on the season one finale of 'The Last of Us'

Ashley Johnson plays Ellie's mom who we meet at the start of episode nine.

Johnson brought Ellie to life in the "TLOU" video game series through voice and motion capture performances. In the video game universe, players learn her name's Anna. It's mentioned briefly on the show.

You can see the rest of the "TLOU" cast here.

Ellie's mom, Anna, seeks shelter in a farmhouse to escape an infected and give birth to Ellie.

Without revealing too much, the house resembles the same one in which Ellie eventually makes a home inside in "The Last of Us: Part II." In the game universe, the farmhouse isn't far from Tommy and Maria's Jackson community in Wyoming.

At the episode's start, we see Ellie and Joel near signs for 80 west and 15 north. The two highways converge at Salt Lake City, Utah.

This aligns with the video game, which brings the pair to Salt Lake City, Utah. In the game, the fictional Saint Mary's Hospital serves as the Fireflies' base and lab.

For those following along, Joel and Ellie have traveled roughly 3,534 miles, according to Google maps, across the first season. They began their journey in Boston on episode one.

The above map tracks their journey starting in Boston and moving across Lincoln, Massachusetts (episode three), Kansas City (episodes four and five), Cody, Wyoming (mentioned in episode six), Jackson, Wyoming (episode six), Boulder, Colorado (end of episode six), Silver Lake, Colorado (episodes seven and eight), and Salt Lake City, Utah (episode nine).

If you count their journey back to Jackson at the episode's end, they traveled over 3,700 miles on season one.

The finale implies that Ellie's immunity is linked to her mother, Anna, getting bit by an infected in the moments leading up to Ellie's birth.

As a result, it's presumed that Ellie has some built in immunity to the infection or a mutation of the fungus, but we never receive a definitive answer.

"It does hint at and give some theories as to why Ellie is immune, even though we don't answer that conclusively," Druckmann told press in a conference for the finale, according to The Hollywood Reporter.

After tests are run on Ellie at the hospital, Marlene tells Joel the following:

"Our doctor 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. It's why she's immune."

In the game, a surgeon's recording says the cause of Ellie's immunity "is uncertain"; however, Marlene tells Joel there's a cordyceps growth inside of Ellie they "believe" mutated. We never learn in the game how Ellie wound up with that growth. Fans merely theorized that her mother was bitten while pregnant or that Ellie's father was infected at the time of her conception.

On the official "TLOU" podcast, coshowrunner Neil Druckmann revealed that he wrote a short story origin for Ellie a long time ago and attempted to have it made into a live-action short.

In the finale episode, Ellie and Joel happen upon a group of giraffes and feed one.

Those who have played the game and were waiting for this interaction may have noticed the show hinted a few episodes back at a potential giraffe interaction.

On episode six, the room in which Ellie stayed in Jackson, Wyoming contained a few giraffes. Giraffe artwork hung on the wall and a giraffe stuffed animal could be seen opposite Ellie at one point. That seemed purposeful since the stuffed animal near Ellie is a lion in the game.

In the game, the giraffes are part of the Salt Lake City Zoo. Joel and Ellie pass by ads for it on the street before finding them. It isn't made clear on the show that the giraffes came from a zoo.

Before arriving at the hospital in the game, Ellie hands Joel a photo of him and his daughter, Sarah, that she stole from the Jackson, Wyoming community. Joel gets a bit emotional, but thanks Ellie for the photograph.

In the game, Joel tells Ellie, "No matter how hard you try, I guess you can't escape your past. Thank you."

It's a little weird the game cut this line and moment. Those words eventually come back to bite Joel, foreshadowing events in the second game.

Instead, on the show, Joel revisits their convo from the start of episode three. In that episode, Joel said he received an injury after a guy shot him. That was a lie. The man who shot Joel was himself.

Joel tells Ellie about Sarah's death and explains he couldn't see the point in continuing forward. As a result, he attempted suicide, but flinched and failed.

The two share an exchange where Ellie surmises that "time heals all wounds."

Joel tells Ellie, "It wasn't time that did it," hinting that her presence has helped him immensely and that he wouldn't be able to deal with such a loss again.

On HBO's official podcast, showrunners Neil Druckmann and Craig Mazin said this is their way of saying "I love you" to one another.

This conversation likely leads to Joel's actions at the episode's end when he goes on a murderous rampage at the hospital to get Ellie back before she's killed for a potential cure to the cordyceps' infection.

If you weren't sure why Marlene asked a soldier to give Joel a knife, it's because it belonged to Ellie.

Marlene wanted Joel to have a piece of Ellie even after she was gone. As we learned at the episode's start, that knife actually belonged to Ellie's mom, Anna. In the game, Anna left a knife and letter for Ellie. She carries both with her throughout the games.

In the game, Joel has the option to find one of Marlene's voice recorders, which serves as a living diary to Ellie's mom. On the recording, Marlene says she was tasked with killing Joel, but refused to do so, instead asking for him to be escorted from the facility.

"I'm not about to kill the one man in this facility that might understand the weight of this choice. Maybe he can forgive me," Marlene's recording says.

We never learn that important context in the show, knowledge which may have made show-only viewers think less of Joel when he mercilessly gunned down Marlene at the episode's end. Since you know Marlene spared Joel's life in the game, it makes his ensuing murder of the Firefly leader more diabolical and ruthless.

Druckmann and Mazin revealed on "TLOU" podcast that Bailey, who plays Abby in the video-game sequel, appears as one of the nurses we see on the finale.

Mazin said they pitched Bailey during the final days of the season's production to appear on the show.

"What I got is a nurse, but the nurse is wearing a surgical mask," Mazin said. "And she's like, 'That's even better. I'll just be like this secret cameo that no one knows about,' and now everyone does."

The cameo's even cooler because Bailey played one of the nurses in the first game. Druckmann added that he loved Bailey so much that he knew she had to play one of the main characters in the sequel.

When Ellie awakens in the back of a vehicle near the end of the episode, she's confused as to why she's wearing a hospital gown and why they're on the move. Joel makes up a story of how the hospital was raided and how they barely got out alive. (In reality, Joel went on a murder spree to save Ellie from getting killed to potentially save humanity.)

Joel also tells Ellie that there were others like her and they've given up on a cure. When Ellie asks Joel if Marlene is OK, Joel refuses to respond, instead telling Ellie he's taking them home to Tommy's community in Jackson, Wyoming.

Their car eventually breaks down and the pair continue on foot to the Jackson community. Before they arrive, Ellie stops and confronts Joel. She's unsure of whether or not he told her the truth about what went down at the hospital. She commands him: "Swear to me that everything you said about the fireflies is true."

In both the show and game, Joel hesitates before swearing it's true.

Ellie never asks about Marlene's fate in the video game. Joel's refusal to tell Ellie the truth about killing her may come back to haunt him next season.

On HBO's look inside the episode, Bella Ramsey, who plays Ellie, reveals that her character knows Joel is lying. She was just giving him a chance to come clean.

"She knows deep down that he's not telling the truth," said Ramsey. "But she can't let herself believe it, because it's too painful, and it's too scary, the idea that her only purpose in life hasn't been fulfilled. That that had been taken away from her by the person that she loves and trusts the most. It's too overwhelming. So she forces herself to believe Joel."