[ This article contains SPOILERS for Arrow: Season 5]
When basing a television show on a long-running series of comic books, there is a lot of material to work with. When hundreds of stories are available as source material, choices have to be made about which characters and stories to use, and which to leave out. Then, in order to keep viewers on their toes, choices have to be made about what elements to change. Alter the stories too little and long time fans know everything that will happen. Sometimes, changes are needed. Such is with case with 'Fighting Fire With Fire', the most recent episode of Arrow.
When District Attorney Adrian Chase arrived in Star City around the same time as Vigilante, most people assumed they were one and the same. The timing of their appearances aside, Chase is Vigilante in the books. Though there was some doubt when the promotional material for 'Fighting Fire With Fire' revealed that Vigilante was targeting Mayor Queen for covering up the truth about Detective Malone's death -- a cover up Chase participated in. Those doubts were conformed after Vigilante lost a fight with Prometheus, who then removed his mask. Chase can't be Vigilante. He's actually Prometheus.
In the promo for the next episode, 'Checkmate', it looks as though Oliver learns the truth about Chase, who until now has been a friend and ally. Friend no longer, he's taken Oliver's girlfriend Susan Williams hostage and brags about being "Ten steps ahead" of Oliver. Having been friends for so long has given Chase a good long look at Oliver's life and who he cares about. Considering he's worked closely with Thea and Lance, defended Diggle, and seen Rene and Dinah around the office, Susan Williams will probably not be the only person in Ollie's life who Chase targets.
From the look of things, it will be Talia al Ghul who reveals Prometheus' true identity to Ollie. Since Prometheus is familiar with the same fighting style Talia taught to Oliver, her connection to him has been suspected for awhile. It will be interesting to see Talia in the present-day, as Oliver has had quite a few encounters with her father and sister Nyssa since the last time he saw Talia.
There is also a question as to Vigilante's identity now. If Prometheus is actually the son of Justin Claybourne -- a victim of The Hood -- then Adrian Chase is either a made up name or stolen identity that he used to become D.A. If it is a stolen identity, than it is possible that the real Adrian Chase is Vigilante after all.
Arrow will return to the CW on Wednesday, March 15 at 8 pm.