Oliver is busy climbing a snowy mountain, and that’s why this episode is called “The Climb.” All right, good night folks! Anyway, 48 hours earlier, Oliver delivers a criminal to Captain Lance and is promptly attacked by an assassin who he, at first, thinks is Malcolm Merlyn, but when the other members of the League of Assassins fly in on their Cirque du Soleil banners, it becomes clear this is a deliberate attack. The group strings Oliver up and knocks him out, transporting him to a location where he meets with Nyssa who asks why he hasn’t delivered them Sara’s killer. She informs him he has exhausted Ra’s al Ghul’s patience and has 48 hours to bring them the killer, or they will kill 50 citizens. Specifically his old buddy Maseo, who is now a member of the League, will be doing the killing.
Laurel sits at Sara’s grave and talks to her sister where she’s joined by Thea, who was placing flowers on her mother’s grave. Thea acts unaware of Sara’s death, but Laurel tells her it happened while she was gone, and asks her not to tell anyone. At Palmer Tech, Ray pops in to talk to Felicity, not about work but about their romantic interaction two episodes ago. He reacted poorly but Felicity doesn’t want to hear it, she gets a buzz from Oliver and heads off to the Arrow Cave. Oliver lays out Nyssa’s ultimatum to the team – 48 hours or people start dying. Felicity reassures them Caitlin is working on the sample but they’ll need a contingency plan in the meantime, something Oliver is lacking.
Five years ago in Hong Kong, things pick up after the last flashbacks with Oliver returning to Maseo’s apartment after torturing a man. He reveals that he learned about a company that accidentally created a super virus which they surmise is what China White is after. Maseo says they need to find the virus and tells Oliver that one man’s life isn’t worth the suffering of an entire city (hope you were paying attention, this is important). Back in the present, Felicity talks to Caitlin and gets the results of the DNA tests which reveal the present DNA matches none other than Oliver himself. Dun dun duuuun. We flash to another clip of Ollie climbing the mountain, this time he slips! Back in the Arrow Cave, the group deliberates about who would want to position Oliver against the League, with Ollie thinking it’s clearly Merlyn, though Diggle is dubious. They need to move fast though, because they’re on the clock.
Once more to Hong Kong where Maseo and Oliver have infiltrated BTHK Biotech. They dispatch the guards and Oliver finds the virus container, but it’s empty. Maseo combs through the security footage and finds China White already had someone on the inside to take it. Back in Starling, Captain Lance is on the phone when his wife Dinah has arrived into town, and speaking of the devil Laurel shows up for business talk with her father and sees her mother. Having seen one daughter Dinah asks about Sara, which Quentin answers with what he thinks is the truth but Laurel stumbles over where Sara is.
Oliver works off some steam while Felicity tracks airplanes leaving Corto Maltese and finds one that made its way to just outside Starling the night before Sara was murdered. Oliver and Roy find the pilot and interrogate him, obtaining security footage of the plane from that night where they find not only Malcolm Merlyn getting off the plane but also Thea. (Quick cut, Oliver is still climbing). Diggle thinks since Thea is Oliver’s sister, maybe the DNA thinks it’s him when it’s actually his sister, but Oliver doesn’t want to hear anything about Thea killing someone. Though the evidence continues to point to Thea, Oliver doesn’t want to believe it. That’s when Ray calls Felicity to talk, saying he’s where she is (Thinking she’s at Verdant). Felicity goes to speak with him when he apologizes for his behavior and reveals that he acted so strangely about kissing her because he never thought he’d kiss someone else after his fiancee, who was killed during Slade’s raid on Starling. Meanwhile, Olive returns to his new apartment he shares with Thea where she’s decorating for Christmas and he quizzes her about her relationship with Merlyn, which she dodges with precision.
In Hong Kong, Maseo kidnaps the man who stole the virus. He starts asking him about the Omega virus he stole but the man claims to not know anything about it, so Maseo brings out Oliver and his new found skills to extract the info. In the present, Laurel and Dinah talk in a coffee shop where Dinah says she can tell something is wrong and it has to do with Sara. She has a mother’s intuition after all. Laurel confesses that Sara died but begs her not to tell her father. Meanwhile in Nanda Parbat, Ra’s runs a spar with some ninjas and kills them all with ease. Nyssa returns and tells Ra’s that Oliver’s time is almost up, to which he says she should return to Starling to teach Oliver they only ask once.
Oliver still doesn’t want to believe Thea killed Sara and he and Diggle begin to butt heads over the matter, but even cool headed Felicity tells Oliver the evidence is clear. Diggle coaxes Oliver into interrogating Thea as the Arrow, so he bursts into the apartment and asks her where Merlyn is, though to his amazement she starts to fight him, and fight him well. Just as they spar, Thea jumps out the window and leaps over the balcony.
The next morning Malcolm Merlyn goes to Verdant to confront Oliver, who pins him to the bar and his phone begins to ring. Upon checking, Oliver sees a video revealing Thea as Sara’s killer. Merlyn threatens to reveal this video to the league if Oliver kills him, and reveals he used a plant called Voture which lends the user to suggestion. In addition, Merlyn reveals to Oliver that he’s in a unique position to challenge Ra’s to trial by combat, where he can strike him down and rid the world of all the blood debts under Ra’s, including Thea’s and Merlyn’s. He leaves, happy that he knows he can still get to Oliver through Thea. Oliver muses on Thea being the killer, but he knows he can win in this fight since he knows who and what he’s fighting for.
Oliver continues the torture in Hong Kong and gets to the end of his rope with no answers, which is when Maseo reveals the existence of the Voture. The idea of mind control leaves Oliver speechless, oh how little you know boy, and Maseo worries that the problem isn’t finding China White but that she might find them. Cut to Maseo’s apartment where China White busts in and begins to fight with Tatsu in a fight that even Beatrix Kiddo would have a hard time with.
In the present, Oliver goes to meet Nyssa and they enter a room where Ra’s waits. As Ra’s starts a spiel about Oliver failing to protect his city, Ollie cops to killing Sara, which seems to leave the entire League in disbelief. Oliver challenges Ra’s to trial by combat, which no man has done in 67 years, but he accepts. (Cut to more climbing, lots and lots of climbing). Maseo, who goes by Sirab now after “something happened,” talks with Oliver as the other members of the League depart. He doesn’t want to watch Oliver die but he will be present as a witness, and gives him the location which he says is sacred ground to the League (Home of the Lazarus Pit perhaps? I mean, say if Ra’s died they could easily stick him in the pit. We’ll see.).
Dinah and Laurel go to Sara’s grave where she pays her respects and tries to make peace with her death, reminiscing about the two of them playing dress up as children. Laurel promises her mother she’ll find who did this to Sara, and Dinah asks her to make them pay. Before departing for his “trial,” Oliver goes to see Thea at the apartment where a window repairman has fixed the one Oliver broke, which Thea blames on a Hitchcockian Bird. Thea can tell something is up and Oliver tries to warn her about Malcolm Merlyn, with Thea reminding him not to make her choose between them. Oliver reminds her that he’ll do anything to protect her and embraces her before leaving. One more Hong Kong flashback, Oliver and Maseo return to their apartment to find blood everywhere and Tatsu missing. Akio reveals that China White kidnapped her.
Felicity and Ray talk at Palmer Tech where she tries to extract his secrets from him. Ray reluctantyl reveals his plans, which began with shrinking down computers and he’s moved over to shrinking down weapons. Though OMAC was part of the Queen Consoldiated line, he’s changed the name to A.T.O.M. (Advanced Technology Operating Mechanism), and he wants Felicity to help him save the city. Hoo boy. Meanwhile, Oliver prepares to leave but Diggle doesn’t want him to go, but he knows he has to. Roy is tasked with watching over Thea and Felicity, with her impeccable timing, arrives just in time. She tells Oliver she doesn’t doubt he can win, but she wants him to kill Ra’s if he gets the chance. Ollie tells her two things, he’ll do anything to protect his sister and he loves her, and with that Oliver finally conquers the mountain he has been climbing all episode.
Oliver arrives at the point on top of the mountain, puts his stuff down, disrobes, and chooses a weapon for his trial. As Oliver picks up two swords, Ra’s reminisces about killing his first victim at 11. He talks about the look on the man’s face and the pride he felt for replacing evil with death. “You have taken your last life,” Oliver tells him, “You have lived your last day” Ra’s replies (come on man, that dialogue rules). The fight starts and though Ra’s is unarmed he clearly has the upperhand. Oliver tries to strike him but Ra’s is too quick, plucking one of his swords from his hands and giving him a nasty cut on his wrist. Just when it seems Ra’s will deliver the killing blow, Oliver gets a streak of luck and disarms him, but Ra’s counters by popping Oliver in the neck, stunning him. “Death come for us all,” Ra’s says, before plunging the sword into Oliver’s chest. As Ra’s says a prayer for Oliver’s soul, he flashes back to memories of his departed parents, of Thea, and of Felicity… then Ra’s kicks him off the cliff.