Oliver and Ra’s fly into Starling City via a cargo plane, but naturally things don’t go all those smoothly, as the plane begins to shake. Back in Nanda Parbat, things are slightly more smooth as everyone wakes up from not being dead and Merlyn reveals that he managed to cure all of them, because why not. The next stage of the plan begins as none other than Barry Allen shows up, knocks out the remaining guards, and sets them free. Though no explanation is provided for how Oliver had time to appear in last night’s episode of “The Flash,” Barry does offer the group what they need to hear: Oliver needs them. They all prepare to head back to the plane they arrived on, except for Tatsu who will return to her life of solitude.
Back in Hong Kong, as Akio has just died and General Shrieve appears to have gained the upper hand, Oliver goes into a berserker rage and beats the snot out of Shrieve. He and Maseo take out the soldiers that enter as well. In the present, Ra’s learns that two of the engines in the plane have failed and suspects Nyssa. To save her, Oliver admits to sabotaging the plane and they break out into a knock-down-drag-out. Ra’s beats both Oliver and his daughter, and jumps from the back of the plane with the lone parachute, as well as the virus. Oliver heads to the front and takes the controls, landing them in a field outside of town. Once more to Hong Kong, Akio has been cremated and his remains placed in three urns, one for Maseo, one for Tatsu, and one for Oliver, who reluctantly accepts. Afterward, Oliver goes back to the bound General Shrieve and starts using the skills Amanda Waller taught him.
Everyone has arrived back in Starling and assembled at Palmer Tech, where Merlyn reveals that they are Oliver’s backup plan. Ollie and Nyssa show up where he is promptly slugged by Diggle. Oliver tries to explain his plan to the no-longer-trusting-him Felicity and Diggle, which involved sabotaging the plane in the hopes of killing Ra’s, destroying the virus, and sacrificing himself. Felicity gets up in his grill about that plane, prompting an overall apology from Oliver, but it doesn’t hold any water at the moment. Flashing back yet again, Oliver holds a bloody hammer as Tatsu is bewildered about what he’s doing, which is in a word, wrong. Maseo reveals Shrieve is still alive, but not for long, as he puts a bullet in his head.
Felicity and Ray continue to look for Ra’s in the city, but he’s so old school it’s hard to even find him. Eventually she finds reference to Damien Darhk in the top floor of a nearby hotel, which has the whole team head off to investigate thinking that Ra’s will kill two birds with one stone by destroying Starling and his rival. Diggle, Merlyn, and Nyssa take out the guards while Oliver busts into the top floor, only to find Darhk is long gone and one of his employees taunting him. He only gets a few lines out though before someone off-screen kills him, but Ra’s calls his phone and delivers a message to Oliver: the virus is in four locations, go get ’em buddy.
Laurel goes to tell her Dad, but he doesn’t want to hear from her. She confronts him about falling off his sobriety, which seems very out of place at the time, but she also tells him that she loves him despite that he might not. Oliver goes to Palmer Tech, where Ray reveals that he’s found a way to neutralize the virus once they’ve located it, and Felicity has a way to locate it. Once more to Hong Kong, Maseo leaves when Tatsu needs him the most, but since he couldn’t save is own child he can’t be with her. It’s a strange mirror version of the Laurel/Quentin scene from moments before. At Palmer tech, Oliver sits and Felicity comes in to talk. He tells her about the recurring dream he has, where he either dies by Ra’s hand or he and Felicity make it out of Starling and go far away. She tells him since he couldn’t beat Ra’s as Oliver or the Arrow, he has to become something else (huhu where have we heard that?), because he’s no longer either of those men. Her phone beeps, revealing the locations of the virus.
Lance gets the locations from Felicity and relays them to the cops, but Oliver, Laurel & Nyssa, Merlyn, and Diggle are all on stand by at the locations. A member of the league appaers to Oliver and tells him Ra’s is waiting for him at the Starling City dam, since he knows Oliver thinks he can win and Oliver knows that Ra’s will never stop. Meanwhile, Diggle goes after a suspicious character with a metal briefcase. Though he catches him, Diggle gets popped by the briefcase and takes a tumble, but the League member takes three arrows to the back, courtesy of Thea in her new masked archer duds. When Diggle opens the briefcase, he is greeted by absolutely nothing, and the league member opens up his throat, because he was the weapon himself.
Oliver goes to the dam to confront Ra’s, who thinks he’s got this one wrapped up no matter what happens. People start falling over all around Diggle, as the virus begins to spread once the infected blood makes contact with the air. Back at the dam, Oliver takes out the sword that pierced him and he and Ra’s begin to fight, again. Across town, Merlyn and Laurel take out the other two virus carriers, and Ray begins to work on a way to get his nanotech airborne to deliver the inoculant. The fight on the dam continues as Lance and other cops watch from a distance, with orders that say shoot to kill. He calls Felicity to let her known, and she begs Ray to fly out there and save Oliver. Ray, however, has to work on the nanotech and save the thousands of infected. Just when it seems Ra’s has Oliver pinned, he cuts down the head of the demon, and is promptly shot by the police. Ollie tumbles down the dam but is rescued by Ray, except after they land we see it was Felicity piloting the suit!
The outbreak is contained, and we learn that Oliver survived the gunshots thanks to his League of Assassins armor. Nyssa is mad that he took Ra’s life, an honor she wanted, but she lets it slide. Oliver delivers a post-game speech to his team about how he originally wanted to do all this alone, but he couldn’t have tonight without his team. He can’t be a hero anymore though, because Ra’s took it from him, instead he wants to accept what is in front of him and run away with Felicity. Diggle takes off in a huff, and Oliver tries to smooth things over (poorly). John can’t trust him anymore. Luckily, Oliver isn’t asking him to get over what he did. They shake hands and John leaves, with Oliver telling him he’ll need a mask if he wants to keep fighting crime.
We return to Hong Kong for the final time as Oliver sees Tatsu off back to Japan. She asks him where he will go, but he says not back to Starling. Merlyn goes to Thea and Oliver’s loft and reveals he’s also leaving town. Oliver comes downstairs and tells Thea to be safe. She asks if she can be called Red Arrow, but he says he already told everyone to call her Speedy (bringing everything full circle for the comic readers). He turns to Merlyn and hands off something to him, something they agreed on, but Oliver tells him he’ll never forgive him, and perhaps now they’ll be enemies once again. At Palmer Tech, Ray does another experiment, saying he had a breakthrough and has the idea to introduce the miniaturization of key components into the suit. As he tests it, however, the entire top floor of the buiding gets blown out in a cloud of smoke.
Back in Nanda Parbat, we see that Oliver handed Merlyn the giant Bugle-like finger ring of Ra’s al Ghul. Nyssa enters and basically rolls her eyes at Merlyn’s plan, but he reveals that technically he fits the prophecy too, since Ra’s tortured him with his own blade and he survived. She’s not happy about this naturally, and vows not to show him mercy. As the other assassins kneel before the new Ra’s al Ghul, Nyssa follows suit. Meanwhile, in a modified version of the opening monologue, Oliver says its time to become something else, and that something is happy, as he and Felicity drive off into the sunset together.