“Unthinkable” is episode twenty-three of season two of Arrow and the season finale.
In the previous episode, “Streets of Fire”, Blood returned the Mirakuru cure Slade stole – Blood never wanted Starling City destroyed. Isabel killed him for doing so. Oliver stuck the cure into Roy, and this episode opens with them worrying it hasn’t worked. Felicity points out Roy does have a lot of Tibetan pit viper venom in him still. An alarm goes off and Felicity says she set up a proximity alarm just in case Slade’s goons came there to kill them. And informs the others that Slade’s goons are there to kill them. Roy stands up at this point, just as one comes through the hatch in the floor, and Roy punches him. Hurting his fist. Looks like the cure worked. They flee on a zip line and an A.R.G.U.S. helicopter arrives just as the Mirakuru thugs are crowding the place. A missile is fired from the helicopter, killing them all – fired by Lyla.
Arrow Base is trashed; Oliver was right about it being compromised. Oliver tells Lyla that Waller is going to bomb the city at dawn. Dig says Waller has never seen a problem she didn’t think couldn’t be solved with a drone strike. Lyla knew, and came anyway because of Diggle. Oliver wants her to go back to A.R.G.U.S. to stop Waller and buy enough time; Diggle is going to go with. Oliver wants weapons salvaging, especially injection arrows, as the cure clearly works. He wants to end it without more killing.
At the end of the previous episode, Thea had shot Malcolm Merlyn twice. She drops the gun and walks away, but Malcolm gets up and calls her name. It’s called Kevlar. No, he doesn’t want to kill Thea because she shot him. Tommy held a gun to Malcolm’s face as well, but was unable to pull the trigger. Thea is stronger and truly his daughter. He could not be more proud of her. That is probably not something Thea wanted to hear.
Lance is at SCPD where the police are arming and he tries to inspire them. Things outside do not sound good. When Lance gets a call from 1PP – with Pike out in the field, he’s the ranking officer – Lauren goes looking for Sara. Who is telling someone she doesn’t want Lauren to be a part of this. And Lauren is hit with a dart and collapses.
Roy is getting caught up and Dig is saying that Slade has at least 50 human weapons. They need an army. Cue Sara arriving with Nyssa al Ghul and other members of the League of Assassins, and Nyssa says an army is what she’s brought. Felicity feels Sara could have called before inviting seven assassins into their top-secret lair. The assassins come at a price, but Sara reassures Oliver that it’s already been paid. She will do whatever it takes to keep her loved ones safe and hopes Oliver will do the same. To fight the unthinkable, you have to be willing to do the unthinkable. They need to find Slade’s base, by Nyssa already knows Slade is operating out of Queen Consolidated. Oliver asks Roy if he wants payback, and has a new mask for him. Roy calls Thea first, who, of course, isn’t out of the city as Oliver thinks. He wants to meet with her at his place; Malcolm tells Thea that Roy is just like the others.
Slade, when they get to Queen Consolidated, tells Oliver and Sara they must have a lot of faith in the cure if they came alone. At which point the League join the party. Slade flees on his own zip line and Sara takes down Isabel. Who starts gloating about how she beat Oliver – until Nyssa breaks her neck. Telling Oliver his reluctance to do what is necessary is why his city is burning. Oliver needs to get closer to Slade to hit him with the cure.
Laurel tells Lance that Sara was with the woman who took her mother. Then another Mirakuru solider arrives and takes Laurel. At A.R.G.U.S., Waller is told the drone is locked on the target. Lance turns up at Queen Consolidated, and isn’t happy to see Nyssa. But he is willing to work with anyone to get Laurel back. Felicity informs them they have another problem; Slade’s men are gathering by the tunnel. They are going to escape when Waller levels the city; Slade is counting on that. Lance tells Oliver that monsters need destroying, and he should get back in the habit of killing. Felicity disagrees with this but Oliver does not. He has to kill Slade; he can’t cure, capture or outthink him. So, Felicity suggests he makes Slade outthink him.
In order to protect Felicity, Oliver takes her back to the Queen Mansion, saying he has feelings for her. Slade bugged the mansion in “The Promise” – did Oliver ever discover this? Dig and Lyla collect some unusual recruits to help them with stopping Waller and Thea discovers more things that don’t make her happy.
Previously, Oliver had rescued Sara on the freighter but Slade already had the Mirakuru cure and had captured them. Slade is trying the Mirakuru on others but it isn’t working. Oliver tries talking Slade into sanity, but the hallucination of Shado is talking him into killing Oliver and Sara. At which point Anatoly fires the torpedo at the freighter as agreed. The ensuing result is why Oliver assumed Sara was dead – again.
There are fights between Oliver and Slade on the freighter and in Starling City. The only new thread that truly opens up is connected to the island, and does start to explain something that always raised a question.