
At first, Joel and Tess couldn't comprehend why Marlene and the Fireflies deemed Ellie so crucial. However, the climactic scene at the end of the first episode unveiled everything, as the Cordyceps fungus scan on Ellie's body yielded positive results, indicating she was infected. Amid Tess's panic and Joel's astonishment, Ellie explained that she was bitten three weeks prior but showed no signs of transformation. This seemingly impossible scenario in the world of TLOU, where Cordyceps-infected individuals lose consciousness within 24 hours, left everyone baffled.
In other words, Ellie is completely immune to Cordyceps. This explains why Marlene and the Fireflies were determined to protect her at all costs, even willing to exchange valuable supplies with Joel to ensure Ellie's safety. Furthermore, Marlene persuaded Joel and Tess to secretly transport Ellie out of Boston's quarantine zone to a rendezvous point at the Massachusetts State House to join the remaining members of the Fireflies. This marks the beginning of the main storyline of the TLOU series, promising even more thrilling adventures in subsequent episodes.
Where do Joel and Tess need to take Ellie?

As mentioned, Marlene struck a deal with the seasoned smugglers Joel and Tess to covertly escort Ellie out of the quarantine zone in Boston to a prearranged location at the State House in Massachusetts to rendezvous with the rest of the Fireflies. This could be considered an involuntary task for Joel, as he had previously asserted that he had never, and would never, traffic in human lives. However, due to Marlene's injury, rendering her temporarily unable to accompany Ellie, Joel reluctantly accepts the deal.
Upon reaching the rendezvous point, the Fireflies will proceed to take Ellie out west to study her immunity to the Cordyceps fungus. They hope to develop an effective vaccine to combat the devastating pandemic caused by this fungus. Fans of the TLOU series are well aware of whether the Fireflies' plan succeeds or not. However, we won't delve into those details in this article to avoid spoiling the experience for the wider audience - those who are new to TLOU through HBO's series.
Who is Riley?

Riley appears in the expansion pack The Last Of Us: Left Behind, as Ellie's close friend. The game focuses on Ellie's time at the FEDRA military school in the Boston QZ quarantine zone - details depicted in HBO's series.
During their time together, Ellie and Riley's bond transcended friendship. However, during an outing to an abandoned mall, they were both bitten by infected. With nothing to lose, they decided to stay together in their final moments. Yet, only Riley succumbed to infection, while Ellie remained unharmed before falling into Marlene and the Fireflies' hands. This incident occurred just before the events of the main TLOU game series.
In reality, Riley is a member of the Fireflies, under Marlene's command. This, coupled with Marlene's close relationship with Anna, Ellie's mother, explains why the Fireflies' leader knows so much about Ellie. The first episode of TLOU revealed that Marlene sent Ellie to the FEDRA military school to ensure her safety. Ellie and Riley's relationship will likely be explored further in future episodes, as Ellie recounts her past and the tragic accident that led her to discover her immunity to the Cordyceps fungus.
Significance of the song “Never Let Me Down Again' on the radio

One of the final scenes in the first episode is Joel's radio, used as a means of signal exchange with two other smugglers named Frank and Bill. The song played during this scene is “Never Let Me Down Again” by Depeche Mode, released in 1987.
Previously, TLOU explained that within Joel's code, songs released in the 80s carry connotations of danger. Therefore, this segment suggests that Bill and Frank may be in a precarious situation, while also hinting that the next episode will closely adhere to the original, with dangers lurking as Joel sets out to find Bill and Frank.
What happened to Tommy?

Tommy, Joel's younger brother, was his companion on the first day of the zombie outbreak. However, 20 years later, they're not as close, despite Joel's attempts to stay in touch with Tommy through the radio. Tommy's sudden silence for three weeks has Joel worried, prompting him to immediately set out to find his brother.
The opening episode of TLOU provided some insights into Tommy's whereabouts, particularly in the confrontation scene between Joel and Marlene. It seems that between 2003 and 2023, Tommy decided to join the rebellious Fireflies, despite Joel's objections. Joel even blames Marlene for turning his close brother against him.
The relationship and conflicts between Joel and Tommy will likely be further explained in upcoming episodes. Currently, all viewers know is that Tommy is somewhere undisclosed west of Boston.
The Last Of Us episode 2 will air on January 23.
Sources: ScreenRant, HBO