Was Ellie brainwashed by the fireflies? I was in a conversation with a friend about The Last Of Us Part 2, and they brought up this theory: what if Ellie was brainwashed by the fireflies to kill Joel, and upon realizing what she had done, sought to kill each and every firefly, hence the line, "I am going to find and I am going to kill every last one of them." Personally, If she was talking about the fireflies it would seem possible. But, then again, the trailer leaves a lot to speculate. Am I wrong? Possibly. But there is a long time before the game releases.