Left Behind is the prequel story bundled with The Last of Us Part I, played entirely as Ellie. It cuts between July 2033 in Boston, when her best friend Riley turns up and takes her to an abandoned mall, and a winter shopping mall in Colorado where Ellie searches for medical supplies for Joel.
1. Back in a Flash (Colorado Mountain Plaza). 2. Mallrats (Liberty Gardens, Boston). 3. So Close (Colorado Mountain Plaza). 4. Fun and Games (Liberty Gardens). 5. The Enemy of My Enemy (Colorado Mountain Plaza). 6. Escape from Liberty Gardens (Liberty Gardens, with a closing scene in Colorado).
Ellie is a student at the military boarding school inside the Boston zone when Riley, missing for weeks, climbs into her room and reveals she has joined the Fireflies. Riley leads her over the rooftops to Liberty Gardens, a mall they once explored together, and turns the night into an adventure: Halloween masks, a brick-throwing contest, restored power, a carousel, a photo booth, an arcade and a water gun fight. Ellie keeps asking why they are there.
In winter, Ellie hides Joel and Callus in a yogurt shop at the Colorado Mountain Plaza, seals the shutter and goes looking for something to treat Joel's wound. The pharmacy is bare, so she heads for a military medical helicopter that crashed through the mall roof, then fights her way back against infected and the survivors who have followed them.
Ellie is weaker in close fights than Joel, so the Colorado chapters give you a new option: make noise to steer infected into groups of hostile survivors, then pick off whoever is left or slip past while they fight. The Live Bait trophy rewards luring an infected into a human with a brick or bottle.
Riley admits the Fireflies are sending her to another city the next day. When Ellie begs her not to go, Riley tears off her pendant and stays, and Ellie kisses her. Runners drawn by their music break in, and after a desperate escape both girls are bitten. Riley says they can give up or fight to stay together until the end. In Colorado, Ellie gets back to Joel, stitches his wound and drags him away on a sled behind Callus.
Main story
The main story of The Last of Us Part I follows Joel, a smuggler in the Boston quarantine zone, as he escorts Ellie, a teenage girl who is immune to the Cordyceps infection, across the United States to the Fireflies. It runs 12 chapters, from Austin on the night of the outbreak in 2013 to the spring of 2034.
The University
The University sends Joel and Ellie on horseback across the University of Eastern Colorado near Boulder, looking for the science building where Tommy says the Fireflies are based. It mixes quiet exploration with a dorm full of infected and a fight against armed looters inside the lab building.
The Outskirts
The Outskirts takes Joel, Tess and Ellie out of the Boston quarantine zone and across the ruined city toward the capitol building, where Fireflies are meant to collect Ellie. It is where you meet clickers and learn to slip past them with thrown bricks and bottles, on a route through downtown, the Goldstone Building and a history museum.
Image: Naughty Dog / PlayStationThe Quarantine Zone
The Quarantine Zone starts the story proper 20 years after the outbreak, inside Boston's military-run zone in August 2033. As Joel, now a smuggler, you and his partner Tess slip outside the wall to track down Robert, a dealer who owes them guns, and end up taking a new job from the Fireflies.