The episode opens on the Queen Estate, where there's a party going on and Oliver is going to be late. Felicity tells Isabel she's sorry and Isabel asks where Ollie is; there's a quick cut to Arrow in action in the middle of a gunfight.
"Just a little held up," says Felicity.
Back at the crime scene, Arrow is interrogating a suspect he captured, asking where they got the guns. He reaches out to Diggle over the radio, and Diggle says the guns are military hardware, probably stolen.
Back at the party, Ollie finally arrives and get scolded by Isabel, who says being fashionably late doesn't work as well on Wall Street investors as it does in high society circles. Ollie smiles and heads off with Felicity, explaining the night's activity to her.
Alderman Blood walks up to Ollie, having overheard the word "guns," and pumps him for information, saying that the gun epidemic in The Glades is out of control. When Ollie says he's sure the cops are doing everything they can to find the source of the guns, Blood and Laurel, who has joined them, explain that it's a local gang leader calling himself "The Mayor" who is providing the guns. The Mayor wants to create chaos so that he can rule The Glades at the barrel of a gun.
Cut to a club, where The Mayor is shooting up a mannequin. One of his people shows up, unarmed, and when questioned tells The Mayor that his gun was taken by The Hood. Ready to kill the young man, one of the Mayor's aides speaks up, asking for leniency because the man is his cousin, and he brought him into the gang. The Mayor responds by sparing the unarmed man and instead shooting his cousin, then giving the unarmed man the gun with which his cousin was killed and telling him to do better for his family.
At the party, Laurel is drinking when Oliver comes up to check on her. She tells him about the trauma of last episode. Felicity steals him away to talk about something urgent. She finally has pieced together that it's Laurel, not Oliver, that the Canary is following around.
That night, outside Laurel's house, Canary is watching her through the window when Oliver shows up. He chases her into a booby trap he's set, where she's tied up and left on a roof. He asks her who she is, and she tells him that once he knows, his life will never be the same. He takes her wig off, realizing that it's Laurel's sister Sara. She tells him she'll give him some time to let it sink in, but then one of her sonic scream devices, left on the ground between them, explodes.
In the Arrowcave, Felicity is a little thrown by the revelation it's Sara, and Oliver admits having lied about her death--he says that a year after the shipwreck, he met up with her on The Amazo. He doesn't know where she's been all these years; he was sure she was dead.
Diggle starts to badger him for details, with Felicity chiming in occasionally as well. Finally Oliver explodes at them that the Lances were better off not knowing that she was alive.
Diggle is trying to track The Mayor, too; Diggle tells Oliver that he needs to keep fewer secrets.
On The Amazo, Oliver gets a visit in his cell from a man claiming to be in charge of those he killed. He tells Oliver that he'll kill him sooner or later, after Oliver tells him everything he wants to know about what was going on on the island. Ollie tells him to go to hell, and the man shoots him, saying they're already there.
Flash forward to the clock tower, where Sara/Canary and Sin are hanging out. Sin brings burgers, and Canary tells her that she's worried her "old boyfriend" is going to tell her family she's still alive. Sin asks why she doesn't want them to know and Sara tells her that she's not who they remember.
She tells Sin that "no woman should ever suffer at the hands of men."
Diggle meets up with his military contact, who tells him that a crate of weapons was taken from Camp Kirby months ago. He tells her that he wants to bring order to the chaos of warlords and maniacs here, as they did in Afghanistan.
At Queen, Oliver meets with Blood, who is waiting for him with Isabel. Oliver tells him that he was inspired by Blood's words on gun violence and that he wants to help--he wants to sponsor a cash-for-guns event. Blood is doubtful of it at first, but Oliver says he doesn't want his name on the program.
When Blood leaves, Isabel tells him that he can't use company funds to pay for the cash-for-guns event.
At her office, Laurel is listening to music when her boss comes to invite her to dinner. At dinner, she's drinking again. She stops when she realizes that her boss is flirting with her, and excuses herself.
On the way home, she's pulled over and tries to pull the "I'm an Assistant District Attorney" card, but it doesn't fly.
At the Arrowcave, Felicity and Diggle have figured out how they can turn the tracking chip on the crate of weapons The Mayor stole back on. They give Ollie the location to go get them.
At the location, The Mayor sees the beacon activated, smashes it, but it's too late; Oliver is there. There's a lot of gunfire as he makes his way through the room, but The Mayor escapes. Ollie manages to get the weapons back but everyone escapes.
Back at the traffic stop, Officer Daly has called Quentin Lance to pick Laurel up. He feels guilty about having apparently passed his drinking problem along to her. He offers to drive her home, but she storms off.
At Verdant, Oliver is met by Sara, silently. They find a place to be alone and she asks if he told her family she's alive. He says no, and asks her how he lived. She asks what happened to Slade, and he evades the question. He asks where she's been, and she evades it. About a year ago, she said, she started to hear about the vigilante--she knew it was Ollie. Ollie asks her where she learned to fight, and asks why she came back.
She tells him it was the earthquake; that she checked on her family. She's still here, though, protecting them. Oliver asks whether she really came because she was hoping he had told her family.
There's a knock at the door, and it's Quentin. "I'm here about my daughter," he says, and Ollie asks if she's okay. Quentin says he'd like Oliver to talk to her, admitting to his drinking problem while they were gone. He tells Oliver Laurel needs a friend.
In his cell aboard The Amazo, Ollie is crying out in pain, looking down at a tray of meds and medical material on the floor and asking the person in the next cell why they did this. He says they do it to everyone; Everyone in prison has scars on their belly/side like one of the ones we've seen on Ollie.
"Living is not for the weak," the Russian prisoner in the next cell tells him.
He takes the first aid tray and prepares to pull the bullet out of himsellf with a pair of calipers, screaming as he does.
Oliver catches up with Laurel the next day, asking her if everything is okay. She gets upset, saying that she can't believe he went to Oliver. She resents the two of them trying to help her. She says her dad is the one with the problem, not her, and storms off.
Back on The Amazo, Oliver is sleeping off the impromptu surgery. The man comes and says "Now, we can talk." He admits that they've been looking for a grave site for two years, and asks if Oliver found the graves. He's looking for the bones that Oliver, Shado and Slade found; Oliver doesn't respond, but the man knows it's the right island.
At the guns-for-cash trade-in, Roy gives them three guns and doesn't take the money. When Thea and Roy meet up with Sin on the street, Sin intuits that she doesn't know about his role with Arrow.
Blood accosts Oliver on the street where he's waiting near the guns for cash drive. He tells Oliver that it's his job to look out for his people. Oliver tells him that he has two friends--sisters--who are having a hard time. Blood tells him that everyone has a crucible in their lives--that he assumes Oliver's was the island. He says that there are three types of people, defined by tha tkind of experience: those who die, those who are strengthened by surviving and those who get used to the fire and spend the rest of their lives in that state.
Living is not for the weak, Oliver says an old friend once told him. "That's a wise friend," says Blood.
Their conversation is broken up by a gun-toting gang, who blast the area and try to assassinate Blood. Oliver tackles Blood out of the way, saving him, and then takes off after the gunmen--but Sin has been shot and is bleeding.
Channel 52 reports that the gang leader is named "The Mayor," and in the cave, Felicity figures out that it's Xavier Reed, someone whose foster brother is an Iraq vet. They figure out that he hopes to take an arms shipment tonight, but Oliver says he won't.
At the hospital, Roy is watching over Sin, who is unconscious but out of surgery. Thea asks if it's okay to stick around with him. Outside, Canary watches, but leaves when Arrow shows up. He's here to recruit her for "a real fight."
A military convoy pulls up near The Mayor, shutting down their engines and lights. They've already killed the one man in their convoy who wasn't with them; The Mayor takes one of the assault rifles, but the pair of them are jumped by Oliver and Canary, who take out most of the group while the Mayor tries to shoot them down but keeps missing. he fires a grenade at Oliver, which Ollie takes out in midair with an arrow. Another flurry of combat later, The Mayor has lost them. Canary jumps him from behind, intending to kill him for going after Sin. Oliver tells her to let him live, and she considers it briefly; he calls her a bitch and she seemingly snaps his neck, telling him she doesn't like that word and letting him fall to the ground.
Channel 52 reports that there are protests at the S.T.A.R. Labs particle accelerator, and that the Cash for Guns trade-in was funded by an anonymous donor.
Blood enters, with Oliver telling him "One man can change the world," and Blood telling Ollie he's only ther ebecause of him. Ollie tells him he should consider a real mayoral run.
Sin wakes up, telling Roy that she'll keep his secret for saving her.
At the hospital, Oliver asks Sara what she's going to do, since she's acting like a ghost. She tells him they're both ghosts--that they died on the island. He rejects that, saying that she needs to tell her family that she's alive. He tells her that if they knew the truth--that he lied to them about her death--that they'd never forgive him but it would be worth it.
At a support group meeting, Officer Lance is telling the group that he's worried about Laurel.
Back on the boat in the flashbacks, Oliver is taken from his cell. He's taken to a room where he's thrown on the ground and someone walks in--Sara.
In Starling City in the present, The Mayor is still alive--a man walks in with a mask, asking him if he's ready to serve him taking back the city, and shoots him full of a drug he calls "a miracle." The Mayor dies.
He removes the mask, and says, "Bring me another." "Yes, Brother Blood," his henchman says.