The episode opens with Artemis visiting Prometheus and giving him the addresses of several of Oliver's associates. Artemis tells Prometheus she wants to be there when he kills Oliver, but Prometheus says that he's only going to make Oliver wish that he were dead.
Thea throws a major Christmas party for Oliver and the rest of the city staff. Oliver asks Thea if she's recovered from the Dominators' mind games, before Susan Williams walks in as Oliver's date. Felicity's also at the party with her boyfriend Billy Malone. She drunkenly introduces Billy to Curtis and Curtis's husband. Felicity then does a terrible job of covering for Curtis's late nights as Mr. Terrific.
Meanwhile, Rory and Rene are hanging out with Diggle and John Jr. at the Arrow Cave for their own holiday celebration. Artemis arrives with presents for the rest of the team (customized stockings) which delights everyone. Also, Rene hints that he has a kid, but gets interrupted before Diggle can ask many questions.
After Oliver gives a speech at the party, both Susan and Felicity congratulate him (and Felicity awkwards it up for everyone). Curtis leaves the party, because Paul caught him in a lie. When Curtis tries to tell Paul the truth, Prometheus shows up and brutally attacks Curtis. Prometheus leaves Curtis bloodied and unconscious while Paul shouts for help.
Curtis wakes up in the hospital with Paul by his side. Paul asks how Curtis knows how to fight, but Felicity and Oliver show up before Curtis says anything. When Paul goes outside to make a statement, Curtis says that Prometheus must know that he's Mr. Terrific, which means that Prometheus knows the rest of the team's identity.
Afterwards, Billy insists that Felicity stay with him until he catches Prometheus, while Oliver says that Curtis has a drug in his system related to an old case. Turns out the drug was tied to a pharmaceutical company owner named Justin Claybourne that was on....THE LIST. Oliver killed Claybourne in order to stop him from gouging TB medicine four years ago.
Felicity informs the team about Prometheus's tie to Claybourne, so they investigate one of his old warehouses. Prometheus leads Green Arrow into an abandoned office and starts to fight him. Prometheus gets the upper hand, but Wild Dog shoots Prometheus's sword out of his hand. However, Artemis then attacks Wild Dog. Artemis claims that the city needs to be saved FROM Oliver and shoots a flash arrow to cover their escape.
Team Arrow gathers at the Arrow Cave as Diggle starts to round up their loved ones at an ARGUS safe house. They found some ashes at the warehouse, so Felicity has Rene and Rory start a DNA test. Felicty then meets up with Billy, who is one stop behind Green Arrow in their investigation. Billy refuses to give up on the case and then leaves.
Rory calls Curtis to inform Evelyn's betrayal, just as Paul walks into the room with dinner. Curtis finally tells Paul about Green Arrow, but Paul doesn't believe him at first. Curtis tells Paul that being a vigilante is empowering and inspiring, but Paul insists that Curtis stop being Mr. Terrific. Paul gives Curtis an ultimatum: be his husband or be Mr. Terrific.
Felicity finds out that the ashes belong to Justin Claybourne, which makes Rory and Rene second-guess who they're fighting. We get another flashback to Oliver's attack on Claybourne. Oliver didn't kill Claybourne, but gave him an ultimatum instead.
Billy heads to the Claybourne warehouse and finds a lockbox containing a baby picture. He sends a photo of the picture to Felicity just before Prometheus finds him and attacks.
Back in the Arrow Cave, Felicity tries to figure out the link between the baby picture and Prometheus.
In a flashback, we get a little more background on Claybourne: he created weaponized TB to gouge prices and create a need for his TB drug. Oliver swears to kill him, but Diggle warns Oliver that there will consequences to his actions one day.
Chase tells Oliver that Prometheus has abducted Billy and convinces Oliver to put a "Shoot to Kill" order on Prometheus.
Felicity finds out that Claybourne had an son, which leads Oliver to believe that Prometheus is Claybourne's son. Furthermore, Oliver says that Prometheus knows very specific moves, which leads him to believe that Prometheus followed Oliver's training in order to prepare for revenge.
Thea suits up in order to help Oliver find Billy. Thea reminds Oliver that there's two sides to every legacy, two versions of WHAT WE LEAVE BEHIND.
Curtis shows up at the Arrow Cave to help Felicity find Billy. We then see a flashback when Felicity helped Oliver track down Claybourne's secret black market group. Oliver remembers the address to that black market group and realizes that's where Prometheus has Billy.
Curtis finds a body in Claybourne's secret office in the exact position of where he dropped some of Claybourne's guards. Oliver follows a trail of bodies, all of which are in the same position as guards Oliver killed four years ago. Oliver finds Prometheus in the spot that Claybourne died and starts to fight him.
After they crash into a lower floor, Prometheus tells Oliver that he's studied him and will take everything from him piece by piece. Oliver sees Prometheus out of the corner of his eye and shoots him three times in the chest. However, Oliver finds out that it was a trick, and that it was only Billy dressed in a Prometheus costume (with his mouth gagged). As Oliver realizes what he's done, Prometheus warns Oliver that everything he touches dies.
Oliver returns to the Arrow Cave and tells Felicity that he accidentally killed Billy. He explains the situation to the team, and Felicity says this was Prometheus's fault. Oliver tells the team they should get as far away from him as possible. But Diggle stands next to him and says the entire team is where they needed to be.
Curtis arrives home to find Paul packing his stuff. Paul says that he doesn't want to drag Curtis away from his new life, but he also doesn't want to stick around to watch Curtis dies.
Lyla calls Diggle up and asks him to get to the safe house, as something is wrong with JJ. When he gets to the safehouse, a team of soldiers is there to bring Diggle back in.
Oliver shows up at Susan's apartment and says he didn't know where else to go. Oliver admits to Susan that he ruins people's lives. Susan says that Oliver only focuses on the bad and starts to kiss him.
The next morning, Oliver walks to the Arrow Cave and finds...LAUREL waiting for him. And that's it for Arrow until January!