Turns out, Talia Al Ghul and Oliver are not on good terms in the present day and Prometheus’ real name isn’t actually Adrian Chase. In the flashbacks, Oliver continues his mission to take down Gregor.
‘Arrow’ Recap: Season 5 Episode 16, “Checkmate”
Oliver arrives at a monastery on a snowy mountaintop. A group of trainees attack until Talia Al Ghul appears. “Why wouldn’t you warn me?” Oliver shouts at Talia after she admits she knows Adrian Chase is trying to kill him. “Two years ago he sought me out. He’s a man of remarkable capacity,” Talia says after she reveals he’s out for blood because Oliver killed Chase’s father. “I helped him in his pursuit of vengeance because then you killed mine. I want you to suffer.”
Felicity figures out Adrian Chase’s real name is Simon Morrison and Oliver gives the tip to Lieutenant Pike--but it’s too late, Chase has Pike nearly killed. After a psychotic conversation with Adrian Chase in the the hospital, Oliver gets back to the bunker and starts ferociously destroying everything in sight.
Meanwhile, Felicity is hacking homeland security for Helix in exchange for the location of where Adrian Chase is keeping Susan Williams. The whole team goes to the building Felicity finds and Chase has various traps set up. Oliver quickly saves Susan Williams while Mr. Terrific rescues Wild Dog and Dinah, who are trapped in rubble.
This time, Oliver thinks he’s one step ahead of Prometheus. He brings in Chase’s wife, but to his surprise, Chase puts a knife through her chest after she tells him to turn himself in. Arrow and Prometheus go at it, punching each other relentlessly until Talia Al Ghul shows up and puts an Arrow in Oliver’s leg. They kidnap him.
“I don’t believe I taught you how to escape from shackles Oliver,” Talia taunts. “Ra’s al Ghul would be ashamed of you,” Oliver says back.
Chase reveals he doesn’t want to killer Oliver, he wants to help Oliver discover who he really is because Oliver did the same for him.
CLIFFHANGER: Unfortunatley, Simon Morrison doesn't seem to have any connection to the comics. However, In the Season 5 episode 17 promo, Chase tortures Oliver to confess his secret. What secret? Let us know what you think in the comments.