Robert is an arms dealer and smuggler boss in the Boston quarantine zone, and the man Joel and Tess hunt down in The Quarantine Zone. He owed them a cache of guns, sold it to the Fireflies instead and sent men to attack Tess, so the pair go after him at his warehouse on the docks.
Robert is vain and cowardly. He breaks his deal with Joel and Tess, then tries to have Tess killed rather than face them, and even when cornered he tries to talk his way out with excuses and offers. Joel sums him up as a man who manages to annoy everyone he deals with.
Joel and Tess sneak through the slums and into the docks, where Robert's hired guards are patrolling. After you deal with them, Robert empties a 9mm pistol at you and runs. You chase him through the waterfront until he is knocked down in an alley.
Tess breaks his knee and Joel breaks his arm until he admits he sold the guns to the Fireflies. He suggests the pair take the weapons back from the Fireflies by force. Tess shoots him dead, and moments later Marlene arrives with the job that starts Joel's journey with Ellie.
Ellie Williams
Ellie Williams is the 14-year-old girl Joel is hired to smuggle out of Boston, and your companion for most of The Last of Us Part I. She was bitten weeks earlier and never turned, so the Fireflies believe her immunity could lead to a vaccine. You play as her in the winter chapter and in the Left Behind DLC.
Joel Miller
Joel Miller is the man you play for almost all of The Last of Us Part I. A hardened smuggler in the Boston quarantine zone, he takes a job escorting 14-year-old Ellie out of the city, and the drop-off turns into a year-long trip across the country to find the Fireflies.
Malick
Malick is a tough in the Boston slums who tries to block Joel's path in The Quarantine Zone. Tess knows him and sends him back to his seat with a single word.
Mark
Mark is a Boston quarantine zone resident who is only talked about. In The Quarantine Zone, Joel can overhear Ronnie telling a friend that soldiers caught Mark using fake ration cards.