This additional episode, a short prequel, takes place only a few weeks before the events of the main storyline. Ellie and her friend Riley sneak into a locked up mall, where they have a fun time, before things change forever. The DLC 'The Last of Us: Left Behind' was released 8 months after the release of the original game. It adds a small chapter to the overall storyline of the game, filling in some gaps that were left open in the main game.