A van drives through Starling City at night. In the back, Felicity removes a black ski mask and remarks on the insanity of their current plan. Sara and Ollie are with her (Dig is driving) and Ollie reminds Felicity that the plan was hers. She says that she never thought he would listen to her. They arrive at property owned by Queen Consolidated and quickly take out a few security guards before Felicity used technology they got from The Clock Kind to get them inside. Once in, they plan to place C4 around to prevent Isabel from getting her hands on anything there. Felicity is caught by another security guard, who Ollie knocks out and carried outside. The gang drives off, and Felicity uses a thermal scanner to make sure no one is inside. They blow up the building. Isabel is on the news, talking about the explosion and saying that the terrorists will be caught. Ollie, Sara, Felicity, and Dig watch in the Arrow Cave and discuss what Slade's plan might be.
Laurel examines a collection of news clippings about Ollie's return to Starling City and The Vigilante. Laurel visits Quentin in jail. He tries to assure her that everything will be fine, but Laurel is clearly worried. She asks him if he knows who Arrow is, and he promises that he doesn't. She asks about his blonde companion at well, and Quentin again says he doesn't know, right as Sara shows up. He asks his daughters to look after each other. Ollie and Moira meet with Ned to assess the damage Isabel has done to their bank account. She has rendered their stock useless in fighting her to regain control. They will no longer have any income from the company. And they need to move all their assets to protect what they still have from her. However, they need Thea's signature as well as Ollie and Moira's. Ned leaves, and Moira reveals that Ollie's father had an affair with Isabel. Moira tells Ollie to talk to Thea and convince her to sign before they lose everything. Flashback to the island. Sara tends to Ollie's wounds, while Knyazev taunts Ivo and threatens him with torture. Ollie refuses to join in. Ivo says he can help them stop Slade. He has a cure. Ollie goes to Verdant to find Thea, but finds Sara instead. Felicity and Dig show up to get Sara and Ollie. They all walk into the Arrow Cave only to find Deathstroke waiting for them. He immediately shoots at the group. Ollie grabs Felicity and gets her under cover. Sara runs at Deathstroke first as Dig kills the lights, then Dig fights as well. Both are quickly tossed aside. Ollie finally runs at him and gets taken down painfully. Deathstroke leaves.
Laurel arrives at the hospital and immediately begins asking for Sara. She bumps into Sara's doctor, who assures Laurel that Sara is banged up but fine. He also mentions her previous injuries. Laurel asks what he means, and the Doctor explains that Sara is covered in scar tissue, and the only other person he has seen that on was a war veteran. As Laurel walks into Sara's room, she sees her sister's back as Sara puts her shirt on. Laurel takes note of the scars but says nothing about the scars. Sara says she and Ollie were in a motorcycle accident. Ollie walks in and gives Laurel the same story. Laurel makes her excuses and leaves. Outside Sara's hospital room, Laurel flashes back to several memories, clearly having figured out that not only is Ollie the Vigilante, but that Sara is his companion. Ollie returns to Verdant, this time finding Thea. She is still furious at him and tries to ignore him. Ollie tries to remind Thea that their father loved her. She says that he wasn't her father, he only loved her because he didn't know that. She says Ollie is only her half-brother, as was Tommy, who she once tried to kiss. She tells Ollie that her life was finally good, she felt like she might be okay for the first time. But now she knows she will never be okay. It's not in her genes. Dig shows up to get Ollie. In the Arrow Cave, the gang tells Ollie that Slade wasn't in the cave for them; he was there for the skeleton key. This tells them his next move.
At S.T.A.R. Caitlin and Cisco are working late. Cisco tells Caitlin that she shouldn't feel guilty about the people who died in the explosion. They hear a noise and go to investigate. They see a security guard, but he dies in front of them, revealing Deathstroke. They run and he chases them. Caitlin finds a weapon and asks Cisco if he can make it work. Deathstroke sees Caitlin waiting for him. Suddenly, she dives out of the way, and Cisco fires the weapon, hitting Deathstroke, who goes down. Cisco tries to fire again, but the weapon fails and he and Caitlin run again. Deathstroke doesn't follow though; he seems to have found what he was looking for. He leaves with some kind of machine. Arrow and Black Canary arrive too late to do anything, so they immediately turn around and leave, not realizing that Laurel is watching them. Felicity and Dig arrive at S.T.A.R. which is filled with cops. Felicity, Caitlin, and Cisco all know each other because Barry's condition worsened and he is now kept at S.T.A.R. Dig and Felicity ask about what was stolen, but Caitlin refuses to answer, its classified information. Cisco also tells Felicity that Barry's condition hasn't changed, and mentions Iris, who Barry apparently has a "thing" with.
In the Arrow Cave, Felicity has managed to find out that the stolen item was a bio-transfuser, which can allow many people to receive blood from a single donor. They realize that Slade wants to use it to give mirakuru to all the prisoners he previously liberated. Ollie wants Slade to go through with it, he'll have to hook himself into the machine and make the donation himself, which should weaken Slade enough for Ollie to fight. Plus the machine will require a huge amount of power to run, so that is how they can find him. Flashback. Sara wants to listen to Ivo. He shows her that he is dying from some kind of infection. He says in exchange for information, all he wants is a quick death to end his suffering. Sara agrees, and Ivo explains that he was able to synthesize a solution that reverses the effects of mirakuru. He hands Sara a key and explains that the cure is locked in the safe in his room on the freighter. Sara picks up a gun and aims it at Ivo. Ollie goes to see Isabel with Dig in tow. Ollie offers her the chance to do the right thing and says he knows about Isabel and his Dad. Isabel says that she wasn't just an affair with him, they were soul mates. He was packed up and leaving Moira and the kids to be with Isabel. But Thea broke her arm in a horseback riding accident and he chose to stay with his family, even though he knew Thea wasn't his. Isabel was fired the next day. Ollie is surprised that his father knew Thea wasn't his. Security arrives to throw Ollie out. On his way, Ollie calls Thea and begs for five minutes. Meanwhile, Dig got a call from Felicity. Someone wants a meeting with Arrow.
In his cell, Quentin plays Solitaire and speaks to a kind guard. Another prisoner is being escorted to his cell, but suddenly attacks the guard, knocking them out and stealing the keys and a club from one of them. He lets himself into Quentin's cell and beats him, claiming that Arrow and Quentin are responsible for his incarceration. Other guards arrive and pull the prisoner off, as the man continues to swear revenge. Laurel gets out of her car and meets Arrow. She talks about being drawn to him and tells him that she knows. But before she can explain further, Sara calls to tell Laurel about their father. Laurel goes to see her father. Kate Spencer is there and apologizes. Laurel goes into her father's room, where Sara already sits. Quintin insists that he is okay, but won't let Laurel hug him; it would clearly be too painful. Laurel asks Sara to step out for a second. Once they are alone, Laurel confesses that she knows who The Arrow is. Quentin tells her that he doesn't want to know, and that he is more than willing to serve 18 months in jail to protect him. The city needs Arrow, the man under the hood is not important. Laurel goes back into the hallway and tells Kate to release her father, or Laurel will quit and spend the rest of her life suing the D.A.'s office on her father's behalf. Kate agrees, but tells Laurel that she will not always be able to get her way in these matters.
Ollie meets up with Thea as she takes out the trash at Verdant. His phone rings before he can tell her about their father. It's Felicity, Slade powered up the machine. She begs Ollie not to go. Thea leaves during the call. Arrow goes to the source of the power surge and sees all the escaped prisoners hooked to the machine, bleeding from the eyes. He goes to the center of the machine, where the mirakuru-infused donor is. But instead of finding a weakened Slade, Ollie finds Roy there. Slade and Isabel enter, they found Roy, who was so depressed he didn't even put of a fight when they took him. Slade says that disconnecting Roy from the machine will kill him. Arrow shoots at Slade, who deflects with his sword. Isabel shoots at Arrow and they fight, with him eventually knocking her out. Arrow shoots a small exploding device at Slade, and it takes him down for the moment, so Arrow goes to save Roy. Isabel gets to her feet and aims her gun at Arrow, only to be shot twice herself. Arrow looks over and sees Dig has arrived. Arrow escapes with Roy. In the Arrow Cave, Roy is comatose. Sara says that he needs a real doctor, but they can't risk anyone finding out about the mirakuru. Ollie managed to collect some mirakuru, so they can use it to synthesize a cure. Dig and Felicity are upset that Ollie never mentioned that Ivo had made a cure. Ollie explains that he was ashamed, he could have cured Slade but tried to kill him instead. He lost his chance to stop Slade. Flashback. Sara is ready to kill Ivo, but Ollie takes the gun from her. Ivo starts to make a confession to everything, but is stopped by Ollie shooting him. He didn't want Sara to have to take a life. Ollie looks at the group of men with them and asks if anyone can pilot a submarine. Thea goes home to get some things; Moira and Ollie try to stop her. Ollie finally tells Thea that their father knew she wasn't biologically his, but he chose her and loved her anyway. Thea says that just means he's a liar, like the rest of them. She leaves. Felicity brings the mirakuru to S.T.A.R. and gives it to Caitlin and Cisco, asking them to help. Ollie sits at Verdant, depressed about Thea. Laurel finds him there and gives him a big hug. Ollie asks what the hug is for, and Laurel says that Ollie will always be special to her. In his hideout, Slade now has his army of super soldiers, plus one. Slade used the mirakuru to bring Isabel back to life.