Joe Goldberg seems to think of everything when it comes to covering up his murderous side, but there may have been one detail in You's second season that could come back to bite him in the future. The newly released season ends with a cliffhanger that seems to promise more seasons to come (although Netflix has yet to officially pick up a third season), and there's one smoking gun that could majorly threaten Joe in a potential Season 3. So, will Forty's movie expose Joe on You as the killer he is? It definitely feels like something Joe overlooked.
Spoiler alert: This post contains spoilers from You Season 2. At the beginning of the new season, Forty Quinn seems like more of an annoyance rather than any kind of actual threat to Joe, but that all changes in the season finale. Throughout the season, Joe only agrees to help Forty adapt Beck's book, The Dark Face of Love, in order to stay close to Love and keep her happy, but that movie script ends up being his undoing when Forty drugs and kidnaps Joe to force them to work on it. During the acid trip, Forty had the breakthrough that Beck must have been killed by a former lover, and the next morning Candace confirmed that Forty's script was completely accurate in implicating Joe as Beck's murderer.
After a quick trip to see the massively unhelpful Dr. Nicky, Forty realized the truth about Joe's murders and attempted to protect his sister by shooting him. Unfortunately for Forty, Officer Fincher caught him pointing a gun a Joe and quickly shot Forty before Forty could kill Joe. But even though Forty wasn't able to kill Joe, he may still be the key to bringing him down in a potential third season.
The smoking gun is Forty's movie script, which could potentially still get made. After all, Kathryn Bigelow is already attached to direct it, as Forty constantly reminded everyone. Although Joe is not named in the script, Candace pointed out that the story very clearly pins Beck's murder on him, so if other people read or saw the story they would likely come to the same conclusion.
The issue, of course, is how the script will make it to the studio now that Forty and Candace are dead. There is still one other person who could turn the script into a movie, though: Ellie. By the end of the season, Ellie had started a new life in Florida with Joe supporting her every so often with money. She was Forty's assistant up until his death, and actually became a major part of the script-writing process. Although she had to rush out of Los Angeles, there is a solid chance Ellie has a copy of Forty's script and could potentially get it made into a movie, revealing the truth about Joe.
All of this is just speculation right now, as Netflix has not even confirmed if You will get a third season yet, but if it does, Joe really needs to watch his back.