Captain Mastros is the senior FEDRA officer left in the Pittsburgh quarantine zone. He appears only in two artifacts from the Pittsburgh chapter: the Abandon zone note he wrote and the Mob attack note about him.
In the Alone and Forsaken section, the note sits on the office desk at the far left of the bookstore's first floor. Mastros tells Mackenzie the revolt has become a bloodbath, they are about to lose the whole zone, and staying means being lynched. He asks for orders.
In the Financial District, after the first group of hunters, enter a nearby building and look behind a desk on the second floor. A soldier writes this in a FEDRA notebook dated October 10, swearing to track down everyone involved.
The Mob attack note reveals that a mob soaked Mastros and his team in gasoline and burned them alive while celebrating. Only the writer slipped away, and Mastros's request to abandon the zone was never sent.
Henry
Henry is a young survivor from Hartford who is trying to get his little brother Sam out of hunter-held Pittsburgh. He and Joel get off to a bad start in a brawl, then team up to escape the city, and he fights beside you through the end of Pittsburgh and The Suburbs.
Jeremy
Jeremy is a FEDRA soldier in Pittsburgh, mentioned in the Lost Hill note you can find in the Pittsburgh chapter. A squadmate writes that Jeremy and a soldier named Pam were left behind when the hunters took Troy Hill.
Sam
Sam is Henry's 13-year-old brother, a quiet, anxious kid who becomes Ellie's first friend her own age on the road. You travel with him from the hideout in Pittsburgh through the sewers and suburbs in The Suburbs.
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.