"Vendetta" is the eighth episode of Season 1. It aired on December 5th, 2012.
Oliver decides to teach Helena that there is justice outside of revenge after witnessing her try to kill the head of the Triad. Diggle expresses his disapproval, believing that Helena cannot be trusted. Oliver shows Helena that they can bring down her father's business by taking out key players and delivering them to the police. Helena starts to buy in to the idea, but after an impromptu dinner with Oliver, Tommy, and Laurel leads to an awkward moment, Helena abandons Oliver's approach, believing he was manipulating her. Helena goes after the Triad, killing their leader. As a result, China White and her men go after Frank Bertinelli, believing him to be responsible, but Oliver gets there in time to stop them. Oliver also stops Helena from killing her father, but she refuses to forgive him for allowing the police to arrest Frank and threatens to reveal his identity if he tries to come after her in the future. Meanwhile, Tommy finally admits to Oliver that his father cut him off financially, and asks for a job working at the club that Oliver is attempting to build. Walter also learns more about the secret organization that Moira is a part of.
Helena wakes up in the middle of the night and leaves Oliver in her bed to follow a lead on the triad. Just when she was about to shoot China White, Oliver arrives and stops her. Despite her frustration at Oliver for meddling, she agrees to dinner with him to try and convince her to change her ways of achieving justice, but she turns him down anyway. She also says that she is not interested in a relationship.
Diggle, on the other hand, tries to convince Oliver that Helena cannot be saved, but Oliver refuses to listen. He then visits the Bertinelli home again and he brings Helena to the grave of Sara Lance and tells her what happened to them. Their shared grief and guilt over the losses of their loved ones finally convinces Helena to listen to Oliver, who promises to never hurt her like she was before.
Oliver then brings her to his lair and tries to teach her archery, with Diggle still trying to convince Oliver to think things through about her. Meanwhile, Laurel tries to convince Tommy to ask Oliver for a job to help with his finances. Then at Queen Consolidated, Felicity Smoak informs Walter Steele of more information she has found on his wife, giving him a symbol of someone also tracking down the information. Walter, insistent on trusting his wife, threatens to fire her unless she stops digging.
That night, Oliver plans an object "lesson" with Helena. He gives her a crossbow and a fitting costume and they go after Anthony Venza, a drug dealer that works for Helena's father, Frank Bertinelli, who also happens to be on Oliver's list. Successful with their trip, Oliver proves to Helena that they can get their justice without the need for the innocent to get hurt. That night, Helena approaches his father, who tells her about being happy for him and Oliver if it makes her happy. She then watches happily as Frank worries about his loss of Venza's business.
Despite wanting to trust Moira, Walter is still bothered by what Felicity told him, so he later proceeds to search Moira's possessions for any sign of the symbol Felicity gave him. Soon enough, he finds a box hidden in their grandfather clock with the symbol on it. Inside the box is an empty journal, much like Robert's.
That night at the new restaurant in the city, Table Salt, Tommy and Laurel are waiting for a table to be available, which Tommy can no longer pay for to get to sooner. Coincidentally, Oliver and Helena were also going to have dinner there, and when they get introduced to each other, Helena offers to let the couple join them, to which a seemingly bothered Laurel agrees to, and the boys reluctantly oblige to.
After what started as casual chatter among friends lead to awkward revelations: Laurel tells Oliver about letting Tommy work for him at his new club, which Oliver laughs at, saying Tommy usually does not like responsibility; and Helena finding out that Oliver and Laurel were once together, and she was now dating his best friend, to which Helena sounds shocked about.
Tommy walks out of the dinner when Oliver seems to poke fun at the idea of working with him, and Laurel soon follows. He tells her that his frustration was from the fact that she wants to ask Oliver for help, and it soon becomes apparent that he is jealous of Oliver. Helena, realizing that Laurel was the girl Oliver told her about, also leaves, saying that it is apparent that he is still in love with her and that if they don't stop now, she will only get hurt again.
Later, though, Tommy goes to Laurel's apartment and apologizes and bares his insecurities about himself, and the two make up. Meanwhile, Oliver admits to Diggle that he thinks he was right about Helena, and he had only wanted to believe so badly that he could have a companion in Helena that he turned a blind eye on the fact that she is possibly beyond saving.
They are later proven right when Helena goes off on her own and kills the head of the Chinese Triad, Zhishan, and frames his father to China White by leaving one of Zhishan's men alive, telling him to pass on the message, "Bertinelli sends his regards." When Oliver later finds Zhishan's body, he realizes that these events would soon lead to "war", just like Quentin Lance had previously deduced.
Walter, no longer able to keep his curiosity in check, talks to Felicity again and asks her to investigate the journal he found, not without giving her a fair warning about the danger, though, but Felicity insists that she is dedicated to solving the mystery.
Meanwhile, word has already gone out that Zhishan is dead and that Bertinelli may have something to do with it. China White and other Chinese Triad members infiltrate their house, planning to kill everyone in the house. Fortunately, Oliver was already in the house, managing to save Frank. However, as Frank was escaping, Helena shoots him down with her crossbow and tells him about all her pent up anger. Oliver stops her from killing him, though, and she turns on him. Their fight gives Frank the opportunity to reach for his daughter's crossbow and shoot her with it.
Oliver brings Helena back to his lair and treats her back to health. She is still ungrateful, however, and when Oliver tells her that her father is going in jail for a long time and she now has justice, she tells him that she is now more interested in revenge. She also threatens to expose Oliver if he does not stay away. Oliver then lets her leave, but not without saying he truly cares for her.
Diggle then tries to comfort Oliver over dinner. Elsewhere, Felicity reports back to Walter with the journal, revealing that there is a list of names on the journal, hidden in subsonic, ultraviolet invisible ink.
That night, Tommy visits Oliver to apologize and tell him about his situation. When Oliver offers him his trust fund, Tommy refuses, telling him he wants to change, beginning with getting an actual job.
Preparation ran from September 17 until September 26, 2012. Filming ran from September 27 and ended on October 5, 2012.