Editor's Note: The following contains spoilers from Episode 9 of The Last of Us.Flashbacks are always a good tool to tell stories, and The Last of Us has been making large use of them. Series co-creator Craig Mazin has wisely stated that the characters' "past is what informs their future", highlighting the importance of flashback for the show. That's usually true not just for The Last of Us, but for most of us, really, and stories as well, and Season 1 of The Last of Us is full of flashbacks.

The use of flashbacks is also one of the main deviations the HBO adaptation has taken from the original The Last of Us game is the use of flashbacks as a common narrative tool. In nearl every episode of Season 1 we've had at least one flashback sequence detailing a different aspect of the story, and all of them are important and placed mostly in the opening scenes. Of course, the game also makes use of this storytelling tool, too, but not as often as we've seen in the series, and, with that many, it's important to keep things in order so as not to miss any detail. So let's have a look at them in chronological order, shall we?

1968: The Talk Show

No one expected the very first scene in the series to be set so far in the past. In it, we see epidemiologists Dr. Schoenheiss (Christopher Heyerdahl) and Dr. Neuman (John Hannah) discussing the possibility and the risks of a worldwide pandemic, and this was the perfect prologue. Not just for the ties it has to our own recent pandemic, but because it also explains how deadly a fungal disease like the cordyceps could be if it was to spread.

Neuman completely shatters the mood of the show when he states that humanity would simply lose in that scenario, while Murray (Josh Brener), the host, tries to sneak in a little humor to improve the spirits, and Schoenheiss claims that that's an impossible context, as fungi can't survive the temperature of the human body. But that doesn't matter, says Neuman, as there are external factors that can lead to it mutating, such as the rise of global temperature. At that moment, their talk ceases to be a hypothesis and becomes a possibility, and a chilling one at that.

1991: Tommy Is Sent To Desert Storm

In Episode 4, "Please Hold To My Hand", Joel briefly tells Ellie (Bella Ramsey) about his younger brother, Tommy (Gabriel Luna). Tommy is described as being a "joiner", an idealistic person who dreams of saving the world and, to that end, joins various movements. When he turned 18, Tommy joined the army and, in 1991, he was sent off to Desert Storm, a massive military operation that was part of the first Gulf War. Unfortunately, being part of that didn't make him feel like a hero, according to Joel.

September 24th, 2003: The Mycology Professor In Jakarta

The opening scene in "Infected", the series' second episode, is just as tense as the one in the premiere. Dr. Ratna Pertiwi (Christine Hakim) is calmly having lunch in Jakarta, Indonesia, but has her mealtime cut short by government agents. She knows she's done nothing wrong, so where - and why - are they taking her? That is soon revealed when they arrive at a government facility, fully equipped with lab, hazmat suits containment rooms, where she meets one of the first people infected with the cordyceps, a woman who worked in a flour and grain factory. When asked about the best way to deal with this, Dr. Pertiwi is clear: the only way to contain the spread is by bombing the city.

We never get an explanation about how the cordyceps infection began in the game, and now the series works us through it. Jakarta is home to the world's largest flour mill. With so much organic matter around and the rise in global temperature that Dr. Neuman mentioned, it seems the cordyceps did in fact mutate and now are present in most flour-based products. By 2003, globalization was already at top speed, so food was largely imported and exported to and from many places in the world. It wouldn't take long for this to become everybody's problem...

September 26th, 2003: Joel's Birthday and Outbreak Day

Now, back to "When You're Lost In The Darkness", the series premiere. It's a beautiful Friday morning in Texas, and it's Joel's birthday. As expected, he doesn't really care, but Sarah (Nico Parker), his daughter, does. She gets up early to make him breakfast, a little frustrated due to the lack of pancake mix. The duo is joined by Joel's brother, Tommy (Gabriel Luna), and they all go on with their days after breakfast. This also happens to be the fateful day of the outbreak and the rest is history.

Viewers with a keen eye were able to identify a pattern: none of the Millers ingested any products that contained flour. There were opportunities for it (the pancake mix and the raisin cookies in their neighbor's house), but Joel, Sarah, and Tommy avoided all of them while unknowingly also dodging a terrible fate. In Episode 3, Ellie (Bella Ramsey) asks Joel how fast was it for everything to crumble when the outbreak began, and Joel mentions it was very quick. Now we know how quick.

September 30th, 2003: Bill Avoiding FEDRA

In Episode 3, "Long, Long Time", we meet one of the game's key characters, Bill (Nick Offerman). The series largely expands and explains his role, especially his relationship with his husband Frank (Murray Bartlett). When we first see Bill, though, he's not all that sweet. It's Tuesday, four days after the outbreak ("By Monday, everything was gone," says Joel at the beginning of the episode, remember?).

An alienated survivalist, Bill built a bunker under his mother's basement in the small town of Lincoln, near Boston, long before the fall of civiliation, and he uses it to hole up and happily watch as the world crumbles. By then, FEDRA had already taken over the government as an immediate response to the outbreak, leading people who could not fit in a Quarantine Zone to an unknowing slaughter. Not Bill, though, who hides in his bunker and makes his little corner of the town a private paradise, away from all the people he despises. He quickly builds a fence around it and rigs the whole place with booby traps and trip wires, but it wasn't enough to protect him from the outside world. For the best, of course.

2003: The Millers Move To Boston, Tommy Meets Marlene

Back to Episode 4, Joel is telling Ellie about when he and Tommy moved to Boston. Tommy convinced him to join a group that was headed to that city and leave Texas. Having just lost everything after Outbreak Day, Joel agrees, mostly to keep an eye on his brother and keep him alive. That's where they meet Tess (Anna Torv). Later, Tommy meets Marlene (Merle Dandridge), who convinces him to join the Fireflies.

2007: Bill And Frank Meet

Four years after the outbreak, there's very little left of the world as it once was. But one day, someone activates one of his traps. A man named Frank falls in a hole just outside the fence while looking for the way to the Boston QZ. Frank barely survived the fall of the Baltimore QZ and was now caught in someone's trap. As the episode progresses, though, the two men quickly find a connection.

As Bill makes Frank lunch, and they get to know each other, and we get to know Bill a little bit more. We also get to see Frank break through Bill's walls with the simplest words and acts of kindness, something that Bill has likely never gotten from anybody. By the end of the episode, we are all in tears, and for a good reason: theirs is one of the sweetest coming-out stories and love stories on recent television.

2009: Anna Gives Birth to Ellie

One of the promises of the HBO adaptation of The Last of Us was to finally reveal the truth behind Ellie's immunity, and it did. The opening sequence of "Look For The Light", the finale of Season 1, shows Anna (Ashley Johnson), Ellie's mother, fighting to give birth to her daughter. Just as the girl is born, the mother is bitten by an Infected, the cordyceps making its way to the baby via the umbilical cord. Later, Marlene would explain that this makes Ellie's brain think she's the cordyceps, not the actual cordyceps. Either way, Anna had to die so as not to turn into a Clicker, and Marlene, her life-long friend, did the deed. We now know from whom Ellie took her toughness after, too.

2010: Bill And Frank Fight Over Decoration

Three years after meeting, Bill and Frank are now a happy couple living together. Well, not so happy, as they are fighting over decorating their compound. Bill doesn't see the point of doing it, as just the two of them would ever see it, while, for Frank, that's precisely the point. It's their home, so they should cherish it and take care of it.

"Paying attention to things is how we show love," a quote that's easily one of the most beautiful and important in the season already. And, while he has Bill's attention, Frank also makes it clear that they cannot go on being oblivious to the world around them. Community is important, and he plans on making friends in the QZ and even having them over to visit, to Bill's utter horror. Can't hide in your bunker forever, man, sorry.

2010: Garden Party At Bill And Frank's

The very next scene shows Frank and Bill eating lunch with the smugglers Joel and Tess (Anna Torv). For Joel and Tess, this is likely the first time in years that they've had a little peace of mind and the perfect space to wind down a little. And Frank is happy to finally have friends. Not Bill, though, as he keeps his gun visible at all times. When Frank and Tess head inside, Bill and Joel get a chance to talk about working together and establishing trustful and mutually beneficial relations. After a few minutes, Bill understands that Joel is like him and, when they are about to leave, Joel warns him that there will be bad people coming for them and that they will need help. Bill understands the threat, and we see later that he fortifies the fence around the compound with stacked cars.

2013: Frank Shows Bill The Strawberries

Three years later, Bill and Frank are having their afternoon jog when Frank decides to show his partner the strawberries he has been secretly growing. He traded one of Bill's guns ("a little one") for the seeds, and now the happy couple can once again enjoy something they haven't had since the world ended. All thanks to having Joel and Tess as friends in the Boston QZ. The world is still bigger than a cul-de-sac, so it's important to have friends - as it always has been.

2013: Raiders Attack Bill And Frank's House

The world is still bigger than a cul-de-sac, which also means there will always be people wanting what you have and are determined to take it away. Bill learns this the hard way when raiders attack his compound. He is shot but rescued by Frank. Thinking he is about to die, he insists his partner calls Joel, who warned him about this risk three years earlier. He has a contingency plan in place, but it also shows that Joel and Tess' relationship with Bill and Frank has continued to thrive.

2017: David and His Flock Leave Pittsburgh Qz

Episode 8, "When We Are In Need", introduced us to David (Scott Shepherd), one of the series' most terrifying villains. He leads a cannibal cult, that Ellie stumbles upon when taking care of a wounded Joel during a harsh winter. They meet on a tense stand-off but find common ground afterward, and David reveals he used to be a teacher before the apocalypse and lived in Pittsburgh QZ. In 2017, though, the conflict between FEDRA and the Fireflies escalated and the city fell to the Infected, and he left with his "flock". He said they moved around but never settled anywhere due to raiders, but it's implied that they were in fact the ones who posed the danger, killing their attackers and, well, eating them.

Early August 2023: Ellie and Riley Go To The Mall

Another emotional flashback, the one in Episode 7, "Left Behind", shows Ellie's last night with best friend and girlfriend Riley (Storm Reid). These events take place roughly three weeks before the events of the main timeline of the series, putting it, probably, on August 8th - we can safely take this guess since Ellie mentions she was bitten three weeks before Episode 1.

The duo goes to an abandoned mall inside Boston QZ, where they have fun and come to terms with who they are to one another. Unfortunately, they also get bitten by an Infected. Riley dies, but Ellie discovers her immunity, setting the events of the series in motion. The purpose of the whole sequence is to inform that Ellie is not giving up yet another person she loves, as Joel lies bleeding after being stabbed in Episode 6.

August 29th, 2023: Joel, Tess, and Ellie Set Out From Boston QZ

The events of the main timeline in The Last of Us start 20 years after the opening sequence in Episode 1, although a precise date isn't provided at first. We later learn that Bill and Frank die together on August 29th, so that's likely the same day they put on "Wake Me Up Before You Go-Go, by Wham!, to play on the radio they use to communicate with Joel and Tess. Earlier that same day, the smuggler duo meets Ellie and agree to take her to the State House in Boston downtown, outside the walls of the QZ. And thus begins their journey.

August 29th, 2023: Bill And Frank's Last Day

Before Joel and Ellie reach Bill and Frank's compound, we see the couple having their last day together. Frank now has cancer and can no longer walk unassisted. Bill takes excellent care of him but has no idea his partner wanted to die on his own terms. When they discuss the matter, Frank asks for a perfect last day, with even a private wedding for them. When it's time to go, though, Bill reveals he also took the pills Frank asked for, so they can continue together even after leaving this world. "You were my purpose," says Bill, and, although reluctant at first, Frank accepts his husband's decision.

Sometime after Bill and Frank go to sleep for the last time, Joel and Ellie arrive. They find Bill's letter, leaving everything for them, and one final lesson for Joel: "I was wrong because there was one person worth saving." Joel and Ellie then get cleaned up and leave with Bill's supplies and aboard his truck.

September 2023: Kathleen and the Raiders Take Over Kansas City

Around one month after Joel and Ellie leave Bill and Frank's, a revolution is taking place in Kansas City. The opening scene of Episode 5, "Endure and Survive", shows how Kathleen (Melanie Lynskey) and the Raiders took over the local QZ from FEDRA, in a violent massacre. The regime they installed, though, was just as brutal and authoritarian, with Kathleen focusing mostly on getting revenge against those who wronged her before, especially Henry Burrell (Lamar Johnson) and his little brother, Sam (Keivonn Woodard). The city quickly earned its new nickname, Killer City.

Late September 2023: Kansas City Falls To The Infected

10 days later, Kathleen and her Raiders continue their search for Henry. That's when the events of Episode 5 take place, when Henry and Sam meet Joel and Ellie and, together, they plan their way out of Kansas City. Things work out up to a certain point, but they are eventually ambushed by Kathleen in the outskirts of the city. A plowing truck crashes into a house in the street they are in, making way for the Infected that were underground to push their way back to the surface, including a Bloater. The Raiders are quickly overrun by a seemingly never-ending amount of Infected, and Kathleen is killed in the skirmish. The four partners are able to flee, but Kansas City is now lost.

December 2023: Joel and Ellie Arrive In Jackson

Three months after the fall of Kansas City, Joel and Ellie finally arrive in Wyoming, as seen in Episode 6, "Kin". In the commune of Jackson, they meet up with Tommy and Maria (Rutina Wesley), as the settlement prepares for Christmas. The next day, our power duo moves on the University of Southern Colorado, where there's supposedly a group of Fireflies who can help them and analyze Ellie's condition. Of course, things go South and the place is now occupied by raiders, who stab Joel as he and Ellie flee.

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