Ellie is a child born to her mother Anna at great risk of being attacked by an infected person and getting infected.

Anna knew that she could not provide a safe environment for her daughter, so she made a brave decision: entrust Ellie to her lifelong best friend Marlene.Marlene assumes the responsibility of raising Ellie, but fate makes them face more choices and sacrifices.Ellie's immunity comes from her symbiosis with the Cordyceps fungus. This secret discovery gives the Firefly Organization hope.They hope to develop a vaccine using the Cordyceps fungus in Ellie's body to save more people's lives.

At the same time, Joel entered Ellie's life.Their meeting was not by chance, but by fate.Joel developed a deep father-daughter relationship with Ellie, and he did not want Ellie to complete a mission that might cost her her life.However, Ellie firmly chose her own path and hoped to contribute to the world.

At the moment of approaching the hospital, the ambush of the Firefly organization made everything complicated.Joel and Ellie were in crisis, and Marlene's appearance gave them hope.However, behind the hope lies a greater sacrifice.Marlene tells Joel that to extract the cordyceps bacteria from Ellie's body, brain surgery is necessary, which means Ellie may lose her life.

Unable to accept this fact, Joel made a surprising decision: to save Ellie at all costs.He grabbed the guard's gun and stormed into the hospital single-handedly, even entering the operating room and shooting the chief doctor who refused to give in.He escaped from the hospital holding Ellie who was in anesthesia and coma, and Marlene's obstruction could not shake his determination.

Joel drove Ellie out of the city. He concealed what had just happened from Ellie, telling her that Fireflies could not make the antidote and had been annihilated by the predators.Although Ellie was dubious, she chose to accept this reality.And Joel was finally freed from the shadow of twenty years.

However, as they were about to return to Jackson, Ellie expressed her feelings of guilt.She hopes that Joel can swear to her that everything about Firefly is the “truth”.Joel was silent for a moment, then simply said: “Yes.”