In the most recent episode of Arrow, "We Fall", Cayden James (Michael Emerson) revealed more details about his crusade against Green Arrow/Oliver Queen (Stephen Amell), specifically that his son had been killed by one of the vigilante's arrows.

However, on the day James insists that Green Arrow murdered his son, Oliver wasn't even in Star City. He had gone to Hub City to recruit Dinah Drake (Juliana Harkavy) to the team, something that Felicity (Emily Bett Rickards) was able to confirm when she reached out to Alena (Kacey Rohl) and learned that James had gotten the information about who killed his son via a USB drive mailed from Corto Maltese. Alena tried to trace the drive to figure out who might be framing Oliver, but was unable to find any information.

But if Oliver physically couldn't have been the person to kill James' son, who might have been behind the murder? Executive producer Marc Guggenheim told ComicBook.com that the answer might come as a shock.

"I think it's going to unfold in a way that will really surprise people," Guggenheim told ComicBook.com. "I actually expect it to be controversial, because we're doing something that's so different than what we've done in years past. There's one particular hard right turn that we've got up our sleeves that we've never done before. So, I'll be curious to see what people think of it."

So, who might be that controversial figure behind it all? We have a few theories.

Vigilante

While Vigilante/Vincent Sobel (Johann Urb) appears to secretly be working against James, that doesn't mean he's pro-Green Arrow. Last season, Vigilante took a very antagonistic stance against the hero, going after criminals in his own way and killing them instead of letting them be arrested or apprehended by Team Arrow. Later, Vigilante took on Oliver Queen directly, targeting the mayor for being corrupt before being cornered by Prometheus and disappearing for a time.

But just because Vigilante gave up last season doesn't mean he had completely abandoned his quest against Green Arrow and Oliver Queen. Vigilante would have had ample opportunity to create a situation that implicated Green Arrow in the murder of James' son. It's an evil scheme made even darker with Vigilante's partnership with James this season.

Prometheus

Adrian Chase may be dead, but the diabolical villain played the long game all of Arrow's Season Five. What's to say that his mission to destroy Oliver stopped simply because he died on Lian Yu? As fans saw with Prometheus' whole "kidnap everyone and blow up an island" method of trying to ruin Oliver's life, the villain would go to any length to ruin Oliver emotionally, heroically, pretty much in any way possible. Killing a child, filming it, and sending the evidence to said child's diabolical father -- while horrible -- isn't something that we can really put past Prometheus.

A Mystery Villain

While it's easy to look at villains we've already seen in action as likely suspects, it's equally as plausible that the show might tap a villain we haven't seen yet for this nefarious plan. It would be a choice that could set the show up for a Season Seven antagonist and could definitely fit Guggenheim's assertion that the person behind everything being controversial, especially if the villain ended up being something from Batman's comic book canon. One Batman villain that might make for a controversial mastermind behind the plot? Hush. In comics Hush/Dr. Thomas Elliot is a brilliant tactician, manipulator and master of disguise -- all skills that would come in handy when setting up the Green Arrow.

Arrow airs Thursdays at 9/8c on The CW.