In The Last of Us, Joel and Tess take Ellie through the destroyed landscape of Boston. Upon getting infected, Tess intends to sacrifice herself so that she can kill an entire swarm of the infected and save Joel and Ellie.
Joel and Tess opt to go through a museum when they find out that their regular route to the State House is filled with the infected.
Since the fungus in the museum is dry and won’t signal the other infected, the path seems safe for them. Taking all the precautions, the trio enters the place and comes across the body of a person who seems to have died recently.
They proceed to walk upstairs. Joel wants all of them to stay silent. Up there, they cross paths with two infected they call ‘clickers’. These infected can’t see but can hear very clearly.
The trio engages in a struggle with these two clickers. In the end, they manage to kill them and come out of the museum alive. The only takeaway is that Ellie has gotten bit again at the same place where she had been bitten earlier.
Tess’ change of attitude
Tess’ behavior abruptly changes following the melee. She is more frustrated. The moment Joel starts suspecting that Ellie might turn due to this second bite, Tess strikes back at him, asking him to take the good news for once.
She stays adamant about taking Ellie to the doctors at the Fireflies’ camp. Though they reach the State House and find the place empty with blood around, she grabs Ellie’s hand and dares to go inside, despite knowing that it’s not the best idea.
The group discovers the bodies of Fireflies. Joel assumes that one of them got bit. The others tried to fight but lost. Tess doesn’t give up. She asks Ellie if she knows where the Fireflies intended to take her.
When Ellie claims that she only knows that they were taking her west, Tess starts searching the bodies, hoping to find a map.
Joel says it’s over, and they should head back home. Tess once again shouts back at him, stating that QZ is not her home. She suggests that their luck had to run out sooner or later.
Joel fails to understand what she is saying, but Ellie figures it out. It turns out that Tess has been bitten too. Joel becomes more careful around her.
Tess shows her bitemark, which has gotten worse. She then tells Ellie to show hers, which, unlike Tess’, has dried out and now looks more like a scratch.
Tess believes that Ellie is, in fact, immune to the fungus. She requests Joel to take her to Bill and Frank. She wants him to convince them to help her.
She has never asked him for anything, not even to feel the way she feels toward him, but now she is asking him to use this chance to keep Ellie safe and set everything right.
An infected wakes up and interrupts their conversation. Joel kills him right away. Since the infected was lying on the fungus, it signals the other infected to come. Soon, a swarm of infected comes storming towards the State House.
Tess knocks gasoline cans and grenades around on the floor, spilling them all over the place. She comes to Joel and tells him to save who he can.
After giving her one last look, Joel grabs Ellie and leaves. Ellie tries to refrain from going, as she doesn’t want to leave Tess behind.
The infected arrive at the State House. They don’t notice Tess at first. Tess attempts to light a flame. One of the infected people corners her, and the tendrils of cordyceps start going inside her through the mouth.
The moment Tess lights up a flame, she drops the lighter. She sacrifices herself and kills most of the infected inside the State House. Joel and Ellie watch the State House burn for a few seconds before walking away.