At Unidac, two scientists are going to their lab and one of them starts to invite the other on a date. As they enter the lab, they discover that the rest of their staff is dead except for the lead scientist, Dr. Markov. The Dark Archer is there and kills him, and then shorts out the doors. Security guards arrive and attack the Dark Archer, who takes them out. He then advances on the two new scientists and kills them. Afterward, Malcolm drives off into the night.
Diggle informs Oliver and Felicity that he's been watching Moira but she hasn't done anything suspicious. Felicity has been monitoring Moira's calls but also hasn’t found anything unusual. Oliver is upset at learning that his mother and his best friend's father are conspiring against the city, and decides to go see Moira and ask her in person as himself rather than The Hood.
As Oliver goes up to the club, he finds Laurel waiting for him. She admits that she hasn't been able to think of much else since Oliver said he still has feelings for her, and Oliver apologizes for making things harder between her and Tommy. Laurel admits that after Oliver disappeared with Sara, she hated him at first. Since he came home, she's had second thoughts because of everything has happened. Laurel considers admitting that she still has feelings for Oliver, but he tells her that he hasn't changed. He turns and leaves to go home and meet Walter.
At the Queen manor, Moira brings Walter in and Thea and Oliver are there to greet him. Walter begs off of brunch and goes to his room to lie down. As he goes, Thea gets a call from Roy asking her to meet him that night. She then points out to Oliver that Walter doesn't seem like himself, and her brother says that he's been through a lot. Thea says that she's sick of them all going through a lot and walks away.
Later, Moira is watching a TV newscast about the slaughter at Unidac. Oliver comes in and asks to talk, but she hastily leaves and says that she has something to do.
The captive Oliver, Slade, and Shado are brought to the camp and taken to the main tent. Yao Fei is waiting with them along with Durand, the man who claimed he was an escaped prisoner. Oliver tries to lunge at the man but Slade stops him, saying they can worry about vendetta later. Yao Fei explains that Fyers was going to firebomb the forest to kill them, and he betrayed them so they'd have a choice. Fyers comes in and Oliver wonders what is going on. Durand is manning the radio and picks up a transmission from a Ferris Aircraft jet, Flight 637 traveling from Germany to Hong Kong. The operator redirects them toward the island and then tells Fyers that it'll arrive in 26 minutes. When Oliver points out that the airliner can't land on the island, Fyers says that he plans to destroy it.
Quentin and Hilton go to the lab and confirm that the arrows used were black, not green. They order a press lockdown and discover that the computer was destroyed and everyone who was working on the current project was killed. Across the street, Roy is sitting in a stolen car with Thea and taking photos. Thea points out that it's been two weeks since they set out to find The Hood and they've had no luck. She assures Roy that he doesn't have to find the vigilante to be someone, but he ignores her and suggests that she uses her connections at CNRI.
That night, Oliver catches up to Moira in the study and asks who took Walter. She says that she doesn't know but he asks for the truth. Moira denies knowing anything about Walter's kidnapping but Oliver suggests that she got in over her head. She tells him to stop but Oliver insists that he needs to know. The power goes out and someone shoots Oliver with a dart. As he drops to the ground, the Dark Archer shoots Moira with another tranquilizer dart.
When Moira wakes up, she discovers that she and Oliver are tied to chairs in a dark room. The Hood Archer tells Moira that she has failed the city.
Fyers explains that a plane crash will ground all air traffic into China, and his employer wants the country's economy destabilized. They will shoot down any jet approaching China and then blame Yao Fei, a former Chinese general. Yao Fei refuses to help and Fyers punches Oliver, shoots Slade in the leg, and wounds Shado in the shoulder. He promises to kill everyone that Yao Fei cares about if he doesn't help.
Thea goes to the police station and demands arrest files to investigate claims of racism. While the officer goes to get the reports, Thea listens in as Quentin and Hilton discuss the case. Markov made several calls to an unclaimed line at Merlyn Global, and Quentin wants Hilton to get someone down from the company to answer questions under oath. She then goes to Roy's house and tells him that the copycat archer is connected to Merlyn Global. Roy wonders what she's planning and Thea figures that they should go there and see what happens.
The Hood tells Moira to explain what The Undertaking is. When she hesitates, the killer beats Oliver but Moira still refuses to talk, saying that Merlyn will kill her and her family The vigilante continues beating Oliver until Moira says that Malcolm has a device that can cause an earthquake that will destroy The Glades. She explains that Robert got involved without her knowledge and his decisions left her vulnerable to Malcolm. The Hood wants to know where the device is so he can stop Malcolm, and Moira says that it's too late. The vigilante cuts Oliver free and then Moira, and she runs to her son. She insists that she didn't willingly become a part of The Undertaking, but Oliver stands up and says that he doesn't know anything anymore, and then limps off.
Oliver goes to the lair and assures Felicity that Diggle didn't hit him as hard as it looks. He has Felicity dig up information on Unidac, and she reports that it specialized in seismic infringement. There's a website claiming that the Dark Archer was responsible for the Unidac massacre, and they realize that the Dark Archer works for Malcolm and is tying up loose ends. They realize that taking out Malcolm won't stop the Dark Archer, but Felicity speaks up and says that she's hacking the Merlyn Global mainframe.
Yao Fei agrees to help Fyers and he takes him off to get into uniform. As Slade moves, Fyers looks at him and Yao Fei slips Oliver a knife. Meanwhile, Fyers calls his employer and tells her that the plan is going ahead as scheduled.
When Moira comes home, she discovers that Walter is meeting with Merlyn. Walter says that Malcolm just came by to set up a racquetball game. Malcolm tells Moira that he's glad to have Walter back where he belongs, and she walks him out. She worries about the massacre and Malcolm says that he had to prevent collateral damage. Moira asks if Malcolm found out what he wanted from Walter, and Malcolm admits that Walter would be dead if he knew the wrong thing.
Tommy comes down to the station to answer Quentin's questions about the phone calls. He assures the detective that he wants the massacre solved as much as anyone, and will be glad to help if Quentin can give him something more than a few phone calls. Laurel comes in and Tommy explains why he's there, and then leaves. Quentin has his CTU tech man Kelton a judge who owes them a favor so they can check Merlyn Global's computers, and then asks Laurel why she and Tommy are on the outs. She finally says that it's Oliver and figures that her father is disappointed in him. He reluctantly admits that Oliver has been different since he got back and invites his daughter out to supper.
Felicity isn't able to hack the Merlyn firewall and she tells them that she has to plug in direct. Oliver says that they'll get her direct access by breaking in.
Later, Oliver enters Merlyn Global and tells the guard that he has an appointment with Tommy. Meanwhile, Felicity comes in as a deliveryman from Carly's diner and says that she has an order for the new security guard. It's Diggle, who has gotten a job as a security guard. He lets Felicity come up and she hands off the bag. She then gets into the elevator with Oliver, but a man gets in before they can shut the door. When he flirts with Felicity, Oliver knocks the man's folder out of his hands and out the elevator doors, and they go up alone. Felicity confirms that Diggle got the drugged hamburger.
Diggle shares the drugged burger with the other security guard and shuts down the security cameras. He then gets Oliver and Felicity to the 24th floor before security locks them out. They climb up the access ladder to the 25th floor mainframe. Oliver fires a crossbow line up and swings to the door, and Oliver tells her that the next patrol will be there in ten minutes. He goes to the meeting with Tommy while Felicity goes to the mainframe room while Diggle monitors her via the security cameras.
Oliver meets Tommy in the conference room and Tommy is surprised to learn that someone put Oliver on his schedule. He doesn't want to talk but Oliver points out that he's still in love with Laurel. Tommy doesn't want to be Laurel's consolation prize but Oliver says that she's no one's property and she chose Tommy. Oliver says that he's not responsible for what happened between Tommy and Laurel and starts to leave, and then asks Tommy what he does there. Tommy says that he works closely with his father and Oliver goes.
A security guard arrives ahead of schedule and Diggle warns Felicity and Oliver. As Oliver heads there, he runs into Malcolm and claims he and Tommy had some unfinished business. Malcolm offers to go down to the lobby with him and Oliver has no choice but to go with him.
Felicity completes the download and gets out, and runs right into the security guard. Diggle calls for Oliver but gets no response, while the security guard demands to see Felicity's ID.
Once Malcolm leaves in the lobby, Oliver starts go to upstairs but Thea approaches him and wonders why he's there. He says that he has to go up and see Tommy, but Thea points out that she just came down.
Diggle picks up Felicity and tells the security guard that she's one of Tommy's bimbos, and escorts her out.
Oliver notices Roy standing nearby and asks Thea why she's really there. She admits that they're trying to find the vigilante. Oliver takes her over to Roy and warns him that The Hood is a psychopath and he doesn't want Thea anywhere near her. As Felicity walks out, Oliver tells Roy to take Thea home.
When Roy and Thea return home, Roy starts coming up with a new plan. He dismisses Oliver as a wimp but she points out that her brother survived five years and was lucky to get him back. Roy says that he lost someone and they didn't come back, and vows to find The Hood so he doesn't lose anyone else. Thea tells him to choose her or The Hood, and Roy says that it's better now than ever. Furious, Thea walks out.
At the manor, Moira checks on Walter. He hands her divorce papers and says that he knows she was responsible for his abduction when he told her about the conspiracy. Moira insists that the arrangement saved his life but Walter isn't impressed. He asks her what she could say that would convince him that his life as he knew it isn't gone, but Moira says nothing. Thea comes in and wonders where he's going, and Walter hugs her. Once he leaves, Moira runs off.
Kelton tells Quentin that he wasn't able to get into Merlyn Global's firewall. However, he detected someone else doing it and traced her to Queen Consolidated.
At the lair, Felicity goes over the download file and explains that she uploaded a virus. Oliver realizes that Robert wanted him to stop The Undertaking, and once he does then it'll be over. Diggle wonders if he plans to retire once Malcolm is defeated, and Oliver says that he came back from the island to stop Malcolm. He then goes to see Laurel and asks if they can talk. She invites him in and Oliver admits that every time they get close, something pulls him away. Now he thinks that the something might be over, and says that Laurel is the most important person in his life. When Oliver hopes that he didn't wait too long to say it, she kisses him and assures him that he's right on time. As they go to the bedroom, Tommy sees them outside through the window.
After sex, Laurel dozes off and Oliver gets a call on his cell phone. It's Diggle, who tells Oliver that they've traced the Markov device to the warehouse in The Glades. Oliver will go after Malcolm while Diggle takes the device. Felicity has confirmed that Malcolm is logged onto his office computer and Oliver heads off.
Yao Fei puts on his uniform and Fyers films his statement taking credit for shooting down the jetliner as revenge against his superiors. Once he finishes, Fyers shoots him in the head. Durand reports that the plane is within range.
Diggle goes to the warehouse and finds the Unidac crates.
Malcolm is in his office and hears The Hood come in behind him. Oliver says that he has failed the city and that The Undertaking is over. Diggle calls and tells him that the device is gone, and Oliver draws an arrow on Malcolm. Malcolm explains that he detected Felicity's virus and says that there's nothing he can do to stop him... and he shouldn't. Oliver fires at him anyway, but Malcolm catches the arrow and throws it back at him. They fight and Malcolm destroys Oliver's bow. He finally knocks him out and unmasks him, staring in shock.