Outside
Joel, Tess, and Ellie head outside the wall to begin their journey to the Capitol Building. When they reach the outside of the wall, they are captured by two soldiers who scan them. Ellie attacks a soldier as he scans her, so Tess and Joel are forced to kill the soldiers. It is revealed that Ellie is infected, but the bite mark on her arm has been present for weeks, while infection and turning normally take mere days. More soldiers show up while Joel and Tess are debating on what they should do, and the three must flee the area before a decision can be made. They escape the wall perimeter as the soldiers are called back.
Downtown
With time to think, Joel and Tess discuss their options. Ellie explains that her immunity could lead to a cure. Joel is against completing the mission while Tess seems hopeful at the thought of a cure. Tess and Ellie begin to walk to the Capitol Building, leaving Joel to follow. They proceed through downtown Boston and reach a large chasm which forces the three to enter an office building that has fallen against another. As they pass through the unstable building they encounter a number of The Infected, including Clickers, and Joel must eliminate several of them so that the group can pass safely. After sneaking through the building and the subway station below, they exit to the streets.
Museum
A wave of Infected chase Joel, Tess, and Ellie into a building. It turns out to be a museum still containing a number of exhibits. Tess and Ellie crawl through an opening that collapses, leaving Joel alone as Clickers appear. He makes his way through the museum to find a Runner attacking a door. Inside he finds Tess and Ellie in trouble as a number of Infected are attacking the two. They clear the area of Infected and continue to the roof.
The Capitol
Joel, Tess, and Ellie reach the Capitol Building but find a dead Firefly near the perimeter. As they enter the building they find that all the Fireflies are dead and Joel and Tess argue about what to do next. Tess frantically searches the body for a map or directions to the lab that Ellie was going to. Joel argues that they are taking this too far, that they should just go home. Tess reveals that she was bitten. She shows Joel her wound and remarks that it is already worse than Ellie's wound, although she was only bitten an hour ago while Ellies was three weeks old. Tess asks Joel to take Ellie to Tommy because he will know where the Firefly lab is located. Joel protests but Tess asks him to do it for her. She says, Theres enough here that you have to feel some sort of obligation to me. Before Joel can answer the military shows up and Tess sacrifices herself to give Joel and Ellie some time to escape into the subway station outside the Capitol Building. They pass through the subway, encountering several flooded sections along the way, before leaving Boston behind for good.