Warning: major spoilers ahead for Episode 5 of Arrow Season 6, called "Deathstroke Returns."
The title of Arrow's latest episode may have been "Deathstroke Returns," but Slade Wilson wasn't the only big character to make a major return to the action. While Oliver and Slade were off on a mission to try and rescue Slade's son, Team Arrow was dealing with the reemergence of Vigilante in Star City. He faced off against Dinah, and their first one-on-one confrontation concluded in the reveal of his identity, and it's not one that many fans could have possibly expected. The man under the vigilante mask is none other than Vincent Sobel.
If that name doesn't ring a bell, it's probably because Vince Sobel isn't exactly the biggest character ever to appear on Arrow. He was Dinah's partner and secret boyfriend back when they worked for the Central City Police Department, but he was seemingly murdered by a bad guy by the name of Sean Sonus years ago. Dinah believed that she saw Vincent shot in the head and killed, right before the malfunctioning S.T.A.R. Labs particle accelerator sent its wave through Central City, turning Barry Allen into the Flash and Dinah Drake ultimately into Black Canary.
Given that Vigilante is a recognizable name in DC Comics canon and was a pretty big deal when he appeared in Season 5 of Arrow, many probably expected him to be a bigger character from Arrow history. Prior to "Deathstroke Returns," he only appeared in one episode via flashback. Of course, it was already unusual that Arrow finished Season 5 without revealing his identity, so the show was clearly doing something new with Vigilante.
Still, executive producer Marc Guggenheim stated back at San Diego Comic-Con that "whoever's behind that mask is a face that is familiar to you," which led plenty of people to assume Vigilante was Tommy Merlyn or Deadshot or some other character who we got to know well in earlier arcs. If anybody guessed Vincent Sobel as Vigilante, I'd say they deserve a lot of credit.
Arrow did deliver a pretty logical explanation for how Dinah's dead partner/lover was actually alive and well enough to enact his own versions of justice on the streets of Star City. As it turns out, Vincent was also affected by the wave that gave Dinah her powers. The timing of the wave somehow prevented the bullet from destroying his brain, and it seems that his metahuman powers prevent him from being killed by bullets to the head. This power was lucky for Dinah, as he stepped in front of her after a young cop attempted to shoot her. Vincent may be off his rocker and attempting to assassinate political figures, but at least he's not entirely gone if he still has an attachment to Dinah.