"I killed Billie!," Oliver confessed to his team right after he went after Prometheus, believing he could take him down that night. But Prometheus was not only sharp; he was also brilliant at strategy. Meanwhile, episode 9 of "Arrow" season 5 also showed Laurel, alive.
Episode 9 began with Evelyn, who joyfully provided Prometheus with all information he needed about the Arrow and his team. Evelyn was eager to kill Oliver, but Prometheus made it clear to her early on that he is not going to kill Oliver; he would just make him feel he had wished he were dead.
At a party at the Arrow Cave, Oliver gave a speech, telling the crowd his all-time favorite movie was "Die Hard," although he watched again the film, "It's a wonderful life" and felt he should commit himself again to Star City. It was also at this time when Felicity introduced Billy as her boyfriend and blew Curtis' cover lies to Paul.
With Felicity's blunder, Paul confronted Curtis, outside the building, about the cancelled dinner and coming home late at night. Just when Curtis tried to explain, he was attacked by Prometheus and landed on a hospital. Arguments between them ensued, forcing Curtis to reveal he has been working for the Arrow. Their lines are intense.
"You can be a vigilante, or you can be married to me," said Paul to Curtis as he was about to leave the hospital room. "But you can't do both," Paul continued as he turned around.
Back to the Arrow team, there were flashbacks some years ago where they learned that Curtis was drugged with dycloseral by Prometheus. Dycloseral is a medicine manufactured by Justin Claybourne that would have supposedly come handy to the underprivileged infected with Tuberculosis during an outbreak.
Claybourne was on Oliver's list and well, it did not turn out alright because Oliver killed him and Clayborne's company went down. Now, the Arrow team thought Claybourne is Prometheus so they planned a raid at his old pharmaceutical laboratory. This part was epic because as soon as Oliver and Rene thought they cornered Prometheus, Artemis appeared and disarmed Rene.
"This city needs to be saved from you," Artemis roared on Oliver. Felicity tried to convince Billy to forget about Prometheus because he has been killing cops. Of course, Billy, being the cop, felt it was his responsibility to capture Prometheus.
So Billy went to the old lab and found a photo of a baby that he sent to Felicity through a phone message. Then Prometheus took him.
As soon as the Arrow team knows that Prometheus has taken Billy, Oliver went to an AK Desmond address, which he just remembered after a flashback. But as Oliver reached the place, everything was reminiscent of an incident where he killed Claybourne. The bodies fell exactly where they were years ago. Prometheus appeared and the duel began. But as Oliver thought he pinned down Prometheus, he realized it was Billy when he took his mask.