Season synopsis
Contains spoilers for this season and earlier seasons.
After a cordyceps outbreak collapses society, Joel Miller survives in Boston’s quarantine zone, smuggling with his partner Tess. The Firefly leader Marlene asks them to escort Ellie, a teenager whose bite does not turn her, out of the city. Tess is bitten in the museum and later stays at the State House to ignite an explosion as an infected horde closes in, leaving Joel responsible for Ellie. In Kansas City, they meet Henry and Sam; after Sam is bitten, Henry kills him, then himself.
Joel treats the trip as a job and later tries to leave Ellie with his brother Tommy in Wyoming, afraid he will fail her as he failed his daughter Sarah. Ellie’s humour gradually changes their relationship. Bill’s letter tells them he and Frank have died and urges Joel to keep Tess safe. In Jackson, Tommy and his pregnant wife Maria have made a settlement, but Joel chooses to continue with Ellie. After he is badly wounded, Ellie fends for herself in winter and escapes David, a preacher whose group turns to cannibalism. They reach Salt Lake City, where the Fireflies are preparing to operate on Ellie.
Marlene tells Joel the operation intended to study Ellie’s immunity and seek a cure will kill her. Joel refuses to leave, fights through the hospital, takes Ellie from the operating room and kills Marlene when she pleads with him to stop. When Ellie wakes, he says the Fireflies found other immune people and abandoned their research, hiding what happened and why he chose her life over their plan. They head for Jackson, where Ellie asks him to swear that his account is true. Joel does; Ellie accepts his answer, and the lie between them remains unspoken.