The episode opens up where last week left off: Nyssa offering to cure Thea in exchange for Merlyn's life.
Oliver tells her to deal with Merlyn himself, and not to involve him or Thea, but she says he's the one who put the ring on Merlyn's hand. She says she wouldn't resort to this if she had any other choice.
Oliver says Thea is dying because of something Nyssa's father did, but Nyssa says she's dying because of what Merlyn did and she's just "following events to their inevitable conclusion."
At a restaurant, The Calculator makes excuses for why he left Felicity and Donna, and says he wants to be in Felicity's life. He tells her that he knows she's "Overwatch," and she starts to leave. He tells her that he wouldn't really have killed anyone last week -- that his crimes are "hacktivism" for long-term gain. He asks her to allow her to prove he's not a bad guy, and gives her a thumb drive with a record of hacks he's committed over the years. He says he hopes she will look into it and that they can have a relationship.
At the Lair, Team Arrow thinks killing Merlyn is a reasonable price to save Thea, but Oliver says he's still Thea's family, and that while his father was a bad person, he would love to have his father back. He says they can broker an agreement between Merlyn and Nyssa -- he gives her control of the League and she saves Thea without anyone else dying.
On Lian Yu, Taiana is upset that Oliver killed her brother; she won't believe her brother attacked him first. Oliver shows her the rock he got from Shado, but she snatches it from him and tells a guard she wants to talk to Reiter.
On a rooftop, Merlyn tells Oliver he doesn't believe Nyssa's cure, and he isn't willing to give up the League to save Thea. He's going to go do something real to save his daughter.
On Nanda Parbat, Laurel tries to talk sense into Nyssa, but Nyssa doesn't believe Merlyn would accept a compromise to save Thea. Laurel tells her that they'll convince Merlyn, and Nyssa brings out a group of henchman to say she better, or they're going to war in Star City.
At the Lair, Felicity comes to see the team, telling them that her father is the Calculator. She says she wishes there was a test they could do to prove her father is who he says he is. Oliver says a test is a good idea for both of them.
Reiter comes to Taiana's cell, and snatches the stone away from her, instructing her that he will spare her life only if she continues to nurse Oliver back to health.
At Nanda Parbat, Nyssa is sparring with her soldiers. Oliver tells her he needs proof that what she's selling is real. She instructs one of her people to get her a small sample, and gives it to Oliver, saying it's not enough to cure per permanently, only to offer assurance.
Oliver, having moved Thea from the hospital to the Lair, runs an IV of the cure into Thea, and her scar disappears almost instantly. Merlyn asks what Nyssa's terms are, and when they can meet.
At Oliver and Felicity's apartment, Donna comes to see Felicity, who tells Donna that Noah -- her father -- is in Star City. Felicity asks if it's possible her father isn't as bad as they thought, but Donna says no: he tells you what you want to hear, and the next thing you know, he's hurt you again. She says, people don't change, even if you want them to.
Nyssa, who still doesn't believe it's possible to resolve the conflict with Merlyn without bloodshed, is waiting for him to arrive. Merlyn comes, but brings a small army with him and soon the various assassins are doing battle. Nyssa, outnumbered, orders her remaining troops to retreat, but Merlyn orders his people to follow her. Oliver blocks Merlyn's path, saying he's not moving, but Merlyn decides to go around rather than continue to argue.
At the Lair, Oliver decides that they have to find Nyssa and Merlyn -- that they can't take on two armies of assassins, but he's not willing to let anyone else die tonight.
Taiana gives Oliver an herb to bring his fever down. He tries to help her through her grief, but she doesn't want to hear about it. He tells her about his father's sacrifice, and that it never gets easier to lose people you love. She says she could see when they first met that he was lost. She tells him an old Russian saying: the same hammer that shatters glass, forges steel -- and she tells him that he needs to get better so that he can save both of them from Reiter.
On the streets of Star City, there are already bodies created as collateral damage. Lance tells Oliver that he has to hurry up and stop the violence. Diggle tells Oliver that he has to face reality: it's time to kill Merlyn.
At Palmer Technologies, Felicity walks her father through the R&D department, stopping to show him a T-sphere, which he asks about. He thanks her for giving him a second chance.
As Nyssa and her group make their way through an alley, Laurel drops down to try and stop them. While the pair argue, they're set upon by a group of Merlyn's men. Laurel buys Nyssa time by using her canary cry, but ultimately the fight spills out into the street. Oliver and Diggle arrive, in costume, and after taking out a number of Merlyn's men, they shoot Nyssa with a tranquilizer gun.
In a cell at the Lair, Laurel asks where the Lotus is, and Nyssa won't tell her. Laurel tells her that she's not acting like herself, but like her father, and that now that he's dead, she doesn't have to be this way.
Later, Felicity wheels in and Oliver tells her how hopeless things seem. Felicity comes to tell Oliver that she brought her father to the lab as a test, and he left behind a device that was meant to steal the data in the room. She recites her mother's line about people not changing. She tells Felicity that she agrees with Diggle about killing Merlyn. Oliver says he's still holding out hope that his sister will never have a chance of a normal relationship with her father.
As they're talking, a sensor goes off: Malcolm is visiting Thea in the sublevel beneath the Lair. Oliver tells Malcolm that it's time for him to give Nyssa the ring, but instead Malcolm reminisces about the first time he met her as a baby. Merlyn tells Oliver that he still doesn't really understand the role the League plays in the world, and that the situation is bigger than him. He reveals to Oliver that he knows about Oliver's son, and that Oliver would never sacrifice his city to save his son, but Oliver tells him that he wouldn't stop looking until there was a third option.
Oliver offers Merlyn the option of challenging Nyssa to a trial by combat, saying that they're all backed into a corner. Later, on a rooftop, the assassins and Team Arrow stand around while Merlyn and Nyssa prepare to battle. Just before they start, Oliver halts it, citing League rules that make him her husband, and thus a suitable replacement to fight on her behalf. He tells Nyssa that if he has to choose between her life and Malcolm's, he'll choose to take on Malcolm.
After a bit of bickering, the two start to square off. Oliver gets the obvious upper hand, but Merlyn refuses to yield, saying that in order to end this, Oliver has to kill him. Instead, Oliver cuts off Merlyn's hand, then knocks him out. He removes the Demon's Head ring from Merlyn's severed arm and presents it to Nyssa, demanding the Lotus. They make the trade, and he tells her that she is Ra's al Ghul. She thanks him, and the assassins in the area bow to her, as does Oliver.
At the Lair, Thea wakes up, confused. Oliver doesn't tell her what happened right away. Felicity asks when they're going to tell Thea about what happened to Merlyn.
At Felicity's office at Palmer Tech, Felicity tells her father that she always blamed herself for his leaving. He says again that he thought going on the run was doing the right thing for them. She tells him she doesn't know if she believes him -- and she brings Lance and a group of cops into the room to take him into custody.
Elsewhere, near a burning fire, Nyssa greets Laurel and Oliver. She tells them that she has learned a lot from them, and when Merlyn shows up, she throws her ring into the fire, revealing that she has disbanded the League of Assassins, and released its forces. No one, she says, will be held prisoner by her father any longer.
After Nyssa leaves, Merlyn tells Oliver that death would be a mercy compared to what he plans to do to Oliver now. Oliver tells him not to threaten him.
Oliver tells Taiana that he promises to free her friends. Moments later, Reiter comes to see them -- they're going to dig at daybreak for what Reiter has been seeking.
At their apartment, Oliver comes to Felicity, who's feeling guilty about putting her father in jail. She says the look on his face will haunt her forever. Oliver tells her that closure doesn't come this easily, so don't fool himself into thinking this is over. She tells him not to feel bad about the thing with Merlyn, and he suggests that they shouldn't wait any longer to get married. She says she's in, and they kiss.
Elsewhere, Merlyn calls a meeting with Damien Darhk, telling him that he knows who Oliver Queen cares about more than anyone in the world. It's not Felicity Smoak, he says: Oliver has a son.