Arrow Season Finale Recap With Spoilers: Unthinkable

The episode opens on Oliver staring into space, convinced that the cure isn't working on Roy. An alarm goes off, alerting Felicity to the fact that a number of Slade's Mirakuru soldiers have arrived to kill them. Roy wakes, punches one and hurts his hand. Oliver fires a grappling line out of the damaged clock face (they're in the clock tower), allowing Felicity and Diggle to get the cure to safety; Roy and Oliver follow them out. A black helicopter hovers near the clock tower and as Slade's goons gather at the broken clock face, a rocket fires out the side of the chopper and takes a group of them out in an explosion. It's Lyla Michaels.

At the Foundry, Diggle and Lyla are going to head to A.R.G.U.S. to try and stop the drone strike Waller is sending.  Oliver tells the rest of the team to gather as many weapons as they can; Oliver plans to put injection devices on the end of arrows and deliver the cure that way. No one else will die tonight, he says. Flashing back the few seconds to where Thea pulled the trigger on Merlyn, he falls. She starts to walk away, but he calls out to her, having worn a kevlar vest for the night's activities. He tells her that she's stronger than Tommy ever was and that he's proud of her. She walks away. At the police department, Lance is handing out weapons -- and then a pep talk -- to the cops, who are scared of the bizarre circumstances they face. He asks Laurel where Sara is. She doesn't know. He's called away. As Laurel enters a hallway, Sara is telling someone that "my sister can't be a part of this." When Laurel calls out to her, she's knocked out by a dart. Back at the Foundry, Roy tellls Felicity that he doesn't remember anything since leaving for Bludhaven.  He asks whether he was unconscious the whole time and she tells him he was out. In Ollie's lair, he's planning with Diggle and Felicity. Diggle says they need an army, and Nyssa shows up with the League of Assassins in tow, saying she's brought one.

Oliver objects to Sara bringing the League into this, saying that whatever they offer comes at a price. Sara tells him that she's already paid it and will return with them after the battle. She's willing to keep the ones she loves safe and hopes he's willing to do whatever it takes. She tells him she's sorry about Moira. Oliver said "whatever it takes" doesn't mean cold-blooded killing but Sara says that to fight the unthinkable, you have to be willing to do the unthinkable. Oliver tells Roy to remember his training, and gives him a mask. He tells Nyssa that the League has to follow his directions and take prisoners; that no one dies tonight. Roy asks about Thea, and Oliver tells him she's fine -- that she was headed out of town before the attacks started. Roy calls Thea anyway, who is still arguing with Merlyn. She takes the call, surprised to hear from him. He tells her that he wants to make sure she's alright, and she says she's fine at the train station. He asks her to meet him, and she says she will. Merlyn confronts her, saying that Roy is no different from Roy or Oliver, that he's been lying to her, too. He tells her that she should only go to Roy if she believes he's different. She says she's going to, and if he follows she'll shoot him again; he tells her that he'll be there when she needs him.

Oliver and company make a rush on Queen Consolidated, where Slade and Rochev are making their command center. They take out a half-dozen Mirakuru soldiers by injecting them with the cure. Oliver finds himself face to face with Slade, Rochev and a number of their soldiers. Slade says Oliver must have a tremendous amount of faith in the cure to come alone, but Oliver says he didn't come alone. A bunch of League members rappel into the room, smashing in the windows. Everyone except Rochev and Deathstroke are quickly cured and knocked out; Deathstroke rappels out of the building while Rochev fights with Canary and Nyssa. They cure her and knock her to her knees, but Oliver stops them from killing her. Rochev starts to monologue about how it doesn't matter because she beat him and took away -- but we never hear what because Nyssa kills her from behind. Oliver is upset, and holds her at arrow-point, but she just walks away. He tells Sara that the process isn't working as long as he can't get close enough to administer the cure, since his reflexes are too fast to hit him with an arrow. Back on the freighter, Slade is preparing to kill Oliver when Anatoli shoots a torpedo through the freighter. In the present day, Lance finds Laurel unconscious and right after she reveals that Sara left with Nyssa, there's a commotion in the next room; it's a Mirakuru soldier, who is knocking out cops (including Lance) in his search to grab Laurel.

Lance joins the group at Queen Consolidated, upset about having to work with Nyssa. He tells them about Laurel, but Felicity picks up thermal imaging; the Mirakuru soldiers are trying to escape the city via a tunnel out of town to avoid being blown up by A.R.G.U.S. Oliver says that the city comes first, and starts to leave, taking Nyssa with him. Lance appeals to him, saying that Wilson and his men are monsters that need to be destroyed. He, too, wants Oliver to start killing again. Felicity tells Oliver that Lance is wrong, but Oliver says he's right. He says he's been fighting with one hand tied behind his back, and that he has to kill him. Felicity says this all started because Oliver tried to kill him last time. She says to make Slade outthink him instead of trying to out-think Slade. At Roy's apartment, Thea shows up as he's watching a news report. He apologizes to her, then starts to move toward her, telling her that he's cured now. She tells him that Sin told her, but asks if he's okay now. He says he's fine -- he lost a lot of time but he's okay. Thea asks about Arrow, saying that he promised to take care of Roy. He tells her that he doesn't know about the Arrow, that he's done with all of that and he only cares about her. She tells Roy they need to leave town and start over. He tells her he's never losing her again, and they kiss. His phone rings, though, and he says there's one thing he needs to do before they go. She doesn't want him to do it. He asks her if she trusts him, and she says yes. He tells her when he gets back, they're leaving forever, and that he loves her. At Queen mansion, Oliver leaves Felicity to keep her safe from Slade. She says she doesn't want to be safe; she wants to help. He tells her that Slade took Laurel because he wants to kill the woman he loves, but he took the wrong woman, and that he loves her. He leaves (apparently still unaware of SLade's listening devices in the mansion).

At A.R.G.U.S., Diggle tells Lyla he loves her. They enter the building. At the main activity room from last time, Waller is having a hard time getting a visual because Gomez and Easy Company have been slaughtered in the tunnel by the Mirakuru Army. Oliver leads the League of Assassins against them, curing them all in one fell swoop. Even Roy can se a bow now. Nyssa is almost killed by a Mirakuru soldier from behind but he's cured by Lance, holding a cure arrow. In the Suicide Squad's holding area, Diggle and Lyla incapacitate a guard and break them Squad out to help them. Back on the Amazo, water is filling the freighter and Oliver is trying to get Sara off the ship and cure Slade. He throws the remaining Mirakuru into a burning part of the ship and Slade retaliates by grabbing Sara and throwing her out of the freighter, where ollie sees her swallowed up in an echo of the pilot. In Roy's apartment, Thea is packing things up when she finds an arrow and quiver. Waller wants to prep the drone to fire right away, but the Suicide Squad storm the room and Diggle tells her to call it off. Waller tells Michaels it's treason, and reveals that Diggle is going to be a father (Michaels is pregnant).

Slade calls to Oliver, telling him to come meet him or he'll kill Felicity. Oliver joins Slade in an abandoned factory. He narrates that if he'd killed Oliver first thing, everything would have turned out differently. Slade is holding Felicity and another man comes out holding Laurel. Oliver tells Slade that Shado would be horrified by what he has done in her name. He tells Oliver that all he's done is fight for her. He tells Oliver that he'll know what he feels like to hate, and now he knows what it feels like to see an enemy so distracted that he doesn't see the real danger. Felicity stabs Slade with a vial of the cure and darts off as he falls. Sara takes out the other Mirakuru soldier from behind, then Laurel kicks him while he's down. Oliver tells Sara to clear the others out, then grabs his bow. In brief flashback, Oliver finds a listening device at the mansion shortly after Slade's visit. On the freighter, Slade asks how many times Oliver is goign to watch Sara die. The two clash in both timelines in an elaborately-choreographed fight. As Slade says that it wasn't the Mirakuru that made him hate Oliver, the drone flies past. Slade tells Oliver that maybe he'll live long enough to see the city burn. In both timelines he seems to get the better of Oliver; in the present, Slade says it can only end if he kills Slade, but that will prove that Oliver is a murderer. In the past, he tells Oliver that he'll keep his promise even if Oliver cures him, so Oliver responds instead by putting an arrow through his eye. Slade falls back into the water, and another explosion rocks the Amazo, separating the pair.

In the present, Oliver uses bolo arrows to tie Slade to a concrete pylon, wher ehe says that whether Oliver kills him or not, he wins. Oliver calls to Amanda to ask her to call off the drones, telling her that Slade's army is taken out and he's captured. Slade asks him what now. At the pier, Sara tells Lance that she chose Nyssa -- that she's deciding her own fate for the first time. She hugs her father and Laurel, telling them she loves them. Nyssa promises that she'll die before letting anything happen to Sara. Sara tells Laurel that Oliver needs her, and gives her the Black Canary leather jacket. Lance tells her not to get any ideas. He collapses on the pier, his broken ribs from the scuffle with the Mirakuru soldier catching up with him. Laurel calls for an ambulance. At Roy's apartment, he finds the quiver with a note from Thea, saying that she is leaving and never coming back; cut to her getting in the back of a car with Merlyn. Roy takes out his new Arsenal mask and looks at it. Slade wakes up in a cell, where Oliver tells him that this is as far from humanity as he can get him. He concedes that he's alive because of Slade, but that he isn't a killer at heart. He says that stopping Deathstroke without killing proves that Slade also helped him become a hero. He thanks him and leaves, with Slade threatening to escape. On the door is the A.R.G.U.S. logo. Oliver tells him that he's in Purgatory, but leaves Slade ranting about how he keeps his promises. He leaves the prison and goes up a ladder, revealing that the prison is underground on Lian Yu. Diggle and Felicity are there, with Oliver telling them that there will be others they have to put here, and other battles to fight -- that the first is getting the company back. Diggle leaves Oliver and Felicity to talk for a moment, where she admits that he briefly had her fooled that he loved her. She says he really sold the act and he says they both did. There's a plane nearby that Oliver says he'll fly back after Diggle declines to give him the news he had about himself and Lyla. Felicity asks when he learned how to fly a plane while stuck on a desert island, and Ollie flashes back to waking up after the battle with Slade; he's on a bed in Hong Kong, and a man takes him to Amanda Waller, who puts him in the back of a limousine and tells him that they have a lot to discuss.