In the finale of The Last of Us, Marlene reveals exactly what the Fireflies intend to do with Ellie, who is immune to cordyceps, the fungus responsible for destroying the world.
Marlene meets Ellie for the first time when she finds her friend and Ellie’s mother, Anna, in a farmhouse, dying. Marlene was late to come to her rescue.
Anna had gotten bit, but she had managed to give birth to Ellie. She assured Marlene that she had cut the umbilical cord before getting bit, which was a lie, and that allowed Marlene to take Ellie under her wing.
Marlene sends Ellie to the FEDRA and finds her again with a bitemark years later in an abandoned mall. Marlene recognizes her and stops the Fireflies from killing her. They study Ellie, who stays alive for three weeks straight, proving that she is immune to cordyceps.
The doctors working with the Fireflies see Ellie as the cure for saving humanity. Protecting her becomes a priority, and when Joel brings Ellie safe and sound to Salt Lake City, Marlene explains to him the procedure Ellie will be going through.
The surgery Ellie will go through
Joel wakes up in a hospital after being attacked by the Fireflies. He immediately asks for Ellie. Marlene assures him that she is fine. When he insists on meeting her, she reveals that he can’t, as she is being prepared for surgery.
Joel asks what kind of surgery, and Marlene replies that their doctor thinks the cordyceps in Ellie has grown with her since her birth. This growth has created a chemical messenger that makes normal cordyceps think that Ellie is cordyceps. Therefore, it doesn’t attack her or turn her, and this is why she is immune.
The doctor is going to remove the cordyceps from her, multiply the cells in a lab, produce those chemical messengers, and then the Fireflies will give it to everyone they can. This might be the cure they are looking for.
Why does Joel stop the Fireflies?
After hearing everything, Joel states that cordyceps grows in the brain. Marlene agrees and stays quiet, suggesting that Ellie might die if this process is carried out. Joel asks Marlene to find someone else, but Marlene stays adamant about her decision, as there is no one else like Ellie.
Joel then turns on the Fireflies and kills anyone who comes his way. Marlene attempts to explain to him that Ellie would have wanted to save the world. Joel doesn’t change his mind. He kills Marlene and gets Ellie out of Salt Lake City.
On their way to Jackson, Joel lies to Ellie. He tells her that the Fireflies already have a lot of people like her and that they have failed to find a cure. He says that he got her out because the raiders attacked the Fireflies.
Ellie still doesn’t know the truth, and maybe she will find out about it sooner or later, owing to how smart she is, and when she does, she may want to go through this procedure for the sake of the world. The question remains who will tell her and help her save the world?
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