Last of Us 2 Theory: The Fireflies Are All Dead | Screen Rant
The Fireflies played a big role in The Last of Us, and even though they’re mentioned throughout The Last of Us: Part 2, many signs indicate the militia group may actually be dead. Given what happened to Abby and Lev directly after they attempted to communicate with who they thought were the Fireflies, it's entirely possible they could have been speaking to another group entirely.
[WARNING: Spoilers for The Last of Us: Part 2 below]
The Fireflies were a paramilitary group largely operating out of St. Mary’s Hospital in Salt Lake City. In The Last of Us, the group was trying to create a cure for the cordyceps infection which had spread across the country. After learning Ellie was immune from these infected spores, the Fireflies planned to use the teenager to try and develop a vaccine, even though going through with the operation would cost Ellie her life and there was no guarantee it would be successful.
At the end of The Last of Us, Joel rescues Ellie upon realizing all of this, but he does so at the expense of the doctor's lives. This set up the plot for The Last of Us: Part 2, in which Abby comes to avenge her father’s death after Joel ruthlessly killed him during his attempt to save Ellie. The Fireflies seemingly disbanded after this brutal setback, but a glimmer of hope is given during The Last of Us: Part 2's story that the group may still be thriving.
Abby learns from Owen, before his death, that the Fireflies were allegedly rounding up new and old members in Santa Barbara. Owen had plans to take Mel, who was pregnant with their child, to the secret location, and he encouraged the rest of their friends to do the same. When Abby eventually escapes the Seraphite island with Lev, she also starts making her way to Santa Barbara.
The two eventually stumble upon an old barracks in the basement of an abandoned house. Using a radio, Abby is able to get in communication with a man who claims he’s part of the Fireflies. He tells her how to find them on Catalina island, explaining that their numbers are quickly growing again. This immediately gives Abby and Lev hope, so they leave the basement and attempt to find the Fireflies' camp. However, just as they exit the abandoned house, they’re met by a group of Rattlers, who seemingly intercepted their radio communication. The Rattlers take the duo into captivity and force them into slavery – that is, before Ellie comes and helps burn down the Rattlers’ mansion
It’s implied that Abby and Lev eventually go after the Fireflies once they escape Ellie, but there’s no official confirmation they found the group. In fact, it's entirely possible that the Fireflies never re-grouped at all. The man on the other side of the radio could have been a Rattler disguising himself as a Firefly in order to track down Abby and Lev. This would explain why the Rattlers so easily found them, mere minutes after using the radio.
Very little was revealed about the Rattlers in The Last of Us: Part 2, even though they are some of the most vicious enemies in The Last of Us franchise. It wouldn't be surprising if groups of Rattlers were using radio frequencies to find more victims, which would explain how they had such a ready supply of bodies in a place that appeared relatively abandoned. Although there’s reason to believe the Fireflies are all dead at the end of The Last of Us: Part 2, without any official confirmation, it’s left up to players to decide for themselves.