Oliver and Diggle face off against the super-charged Darhk. He tells them he's going to regain control of the Rubicon to complete his plan and leaves the two in the crumbling city hall secret basement.
At the Ark, Thea is grieving over Alex's body when Malcolm shows up. He's not happy she didn't take care of Machin and has the ghost soldiers take her into the house.
Felicity is watching the news about Havenrock when Noah walks in to comfort her. She doesn't stay sad very sad very long, because Curtis shows up. Introductions are made and she tells him they have to shut down Rubicon since Noah just put it on an infinite loop. Felicity gets a text from Thea and takes off.
At H.I.V.E headquarters, Ruve tells Damien that Rubicon didn't work because of Noah an dFelicity. Damien has gotten Felicity's hacker ex-boyfriend Cooper Seldon to help take back Rubicon. Ruve is going back to the Ark with their daughter to deal with Anarky.
Lance is watching the news in the bunker when Oliver and Diggle show up. Felicity is right behind, and gives Oliver a hug, glad he's safe. Felicity tells them she heard from Thea and she's going to track where the text came from. She finds the location and Oliver and Diggle head off. Lance wants to go with, but they make him stay.
Flashback to the island. Oliver tells Taiana about her glowing eyes. Soldiers show up and shoot, but the bullets don't affect her. While the soldiers stand stunned, Oliver shoots them.
Thea is tied up in a chair. Malcolm starts telling her more about Genesis. He's worried about Machin and doesn't want another loose cannon in the ark, so he makes her take some of Darhk's vitamins.
Oliver and Diggle arrive at Thea's location but nothing's there. Felicity is sure there is. Arrow discovers a sewer access point that seems out of place. He blasts it open.They enter the ark.
Malcolm is walking with Ruve. She gets a report that two guys dressed in green and black have infiltrated the complex. She is not happy and tells Malcolm to take care of it as she walks off with her daughter.
Felicity loses Arrow's signal once they go underground. She gets a text from Curtis and takes off, leaving Lance to handle Oliver and Diggle.
When Felicity returns home, she find Curtis drinking. Curis tells Felicity he's sorry for her upbringing as Noah and Donna bring their argument to where they're at.
Felicty says she needs to tell her mother something. Donna is getting excited. So is Curtis. They think she's pregnant. Felicity busts their bubble by telling them no, she needs to save the world and Noah has to help. Donna doesn't believe her until she tells her she's working with the Green Arrow. Donna is a little upset.
Noah and Felcity get to working as Curtis admires two hackers going at it to save the world. They are in a hacker fight with Cooper Seldon for control of Rubicon.
Diggle and Oliver are walking around the Ark while Ruve is speaking to the Ark families via closed circuit.
Oliver finds the house where Thea is being held. She's being held by ghosts, but he takes them out. He unties her. She kicks him and points her gun at him, then reports that she's found the intruder.
Oliver tries to talk to her, but Malcolm shows up. He tells Oliver she's been drugged. Malcolm taunts Arrow about not taking him out before. Diggle shows up shooting. Malcolm escapes. So does Thea.
Diggle and Oliver escape too, but ghosts chase after them. There is a shootout going on.They escape to a stairwell, and the ghosts pass them by. They break into the house.
Darhk is impatient with Seldon. He's quesitiong Seldon about his past with Felicity.
Oliver and Diggle determine no on ei s in the house. He's concerned they might not be able to find Thea. Ruve makes an announcement about the two intruders and they they should be killed.
Flashback continues. Taiana wants to take the idol home to save her village.
Malcolm and Thea are in the control center. Ruve wants Malcolm to find Oliver and Diggle. Anarky is hiding in the vents and hears everything.
Felicity and Noah continue to fight Cooper via computer. Curtis comes up with an idea on how to shut down Rubicon. Noah isn't sure about the idea, and Donna tells him to take a chance. This turns into another argument. Cooper hits a button and sends a surge to all of Felicity's electronics. Lots and lots of tech talk. They decide to send the surge right back to him which may cause Rubicon to shut down. It works.
Donna is not happy when Felicity says "thanks, dad." She goes upstairs.
Ghosts are looking for Diggle and Oliver. The family whose house they are in try to rat them out, but are stopped. The dad tells Oliver they haven't taken the pills and believe that Damien is the answer to setting the city free of it's darkness. He asks if Oliver can do the same. The family is tied up.
Flashback. More shootouts as Oliver comes across a wounded man. Taiana wants to kill him to make her stronger since she feels he's already dead.She wants the power his death will bring her.
Donna is upstairs folding clothes. Felicity comes up to find out what's going on. Donna admits that Noah didn't leave them, that she left him.
Oliver asks Diggle if maybe Damien isn't on to something. The ghosts find them and a shootout ensues. Thea shows up and while Diggle deals with the fight inside, Oliver and Thea fight outside. Oliver tells Thea to fight agains the drugs affecting her. Inside Malcolm shows up. Thea comes in and she's about to shoot Malcolm when Machin comes on the television.
He's taken over the control center and has Ruve and her daughter held hostage. He's going to destroy the Ark either way, whether Darhk shows up or not.
Team Arrow has to work with Malcolm and the ghosts to stop Machin. Oliver tells Malcolm to lead an evacuation while the others head to the control center, but Malcolm questions where he's supposed to evacuate them to when the world outside is going to be destroyed. Oliver tells him he has hope that that is not going to happen.
Flashback. Oliver tries to talk Taiana down from killing the guy, but she kills him anyway.
Machin is taunting both Ruve and her daughter when Oliver and friends show up. Machin was about to kill Ruve, but Thea's arrow stops him. Machin warns the team about what's powering the facility and if they shoot wrong, everything goes up in flames. Anarky takes the arrow that was meant for him and tries to stab Ruve, but another arrow from Thea stops him, but hits one of the tanks causing an explosion.
Anarky takes the arrow and stabs Ruve anyway, then a fight ensues. Explosions continue. Malcolm is trying to get people out topside. The center is starting to cave in. Arrow saves the daughter. Anarky escapes. Arrow tries to save Ruve, but the place is about to collapse. There's not enough time to save her, so he and Thea leave with the daughter.
Back at Hive headquarters, Darhk is alerted to the Ark problems.
Oliver and gang return to safety, but explosions have caused some destruction. Arrow lets Felicity know they are safe. She tells him that the Rubicon is out of commission. He adds that people still need saving and still need hope.
Flashback. Taiana is all crazy about the idol. Oliver takes it away from her, but Reiter shows up.
Malcolm returns to HIVE headquarters and tells Darhk about Ruve. Damien says he knows who can get Rubicon back working again, but Malcolm says there is no safe place to go since the ark is destroyed. Damien doesn't care. The world needs to burn anyway.
Donna talks to Noah about leaving for good. Curtis and Felicity speculate about what her parents are talking about. Donna returns to Felicity sans Noah and tells her Noah is going away for a while.
Darhk shows up to ask Felicity for a favor.