As the episode opens, a waitress is accosted by two men in a dark alley. They grab her and start to force themselves on her when Sara -- or what's left of her -- shows up. She beats both men, brutally killing one of them, and then starts to strangle the woman while chanting in tongues until the police arrive.
At the Queen For Mayor headquarters, Thea introduces Oliver to Alex Davis, their new political strategist. Davis wants Oliver to distance himself from the Lance family, because he likens Sara's death on the Queen's Gambit to Chappaquiddick. Oliver dismisses his concerns, but Davis tells him he can't unite the city if he's seen as a playboy. He wants Oliver to distance himself from Laurel.
In the flashback, Oliver finds his way back to the village, where the man who had gone out on the island with Oliver confronts him about the communications gear he found. He has Oliver follow him in to talk to the man in charge -- Baron Reiter, as it happens -- and he's found an intruder: John Constantine.
Back in Star City, Lance has figured out that the mysterious woman killing criminals is an escaped Sara. He's not happy about it, and Laurel says she wants to find Sara before Lance or Oliver does, since they want to kill her.
At Palmer Tech, Felicity and Curtis examine the thumb drive containing Ray's dying declaration. There's some kind of digital noise on the recording that Felicity believes is "more to the message," and she needs Curtis to decode it.
Lance goes to see Darhk, who gives him a mission: head to a federal server farm and plug a device Darhk gives him into a computer.
At the Lair, Oliver and Thea are practicing with escrima sticks. Thea tells Oliver that she doesn't agree with Davis's strategy of distancing Oliver from the Lances, who have always been there when she and Oliver needed them. Their conversation is interrupted by a call from Felicity: a crazy blonde is attacking a nightclub.
Oliver and Thea arrive, and Laurel is already there struggling with Sara. Before they can take her down, though, Oliver is shocked to learn that it's Sara who's been responsible for the attacks and hesitates long enough to let her get away.
Back at the Lair, Oliver quickly figures out how Sara is back, and he's not pleased.
In the flashback, Reiter shows Oliver a map of the island Constantine had on his person. He wants whatever it is that Constantine is there for, and sends Oliver to escort John to get it. When the other soldier objects, Constantine disarms him and uses his gun to disable a vehicle and take Oliver hostage.
In the present, Lance comes to the Lair to rant about Sara's return. He gives Oliver the device Darhk gave him. Felicity identifies it as a delivery device for a virus that will target and delete select files. Oliver says it isn't safe for Lance to try and infiltrate a federal building on his own. He sends him to work with Diggle, who is not happy working with H.I.V.E., the organization that killed his brother. He decides that he's goign to use Lance to take down Darhk.
At home that night, Oliver and Felicity talk about Sara's return on the couch. Felicity thinks it would be nice to not have to say good-bye to their loved ones, but Oliver says it isn't that simple. They try to figure out why Sara had targeted the waitress, and another woman at the nightclub, when she had otherwise only attacked criminals. They realize after bringing the pair of them up onscreen that the two women both resemble Thea. Oliver tries to call her to warn her, but Thea ignores the call because she assumes he's just calling to yell at her for bringing Sara back. Just then, Sara crashes into her apartment, attacking her while speaking in Arabic. After a brief fight, Thea manages to cut Sara and get out of the apartment -- but after falling down the stairs, Thea loses consciousness and Sara flees.
Thea tells Oliver when she wakes up in the hospital that Sara's going through the same thing she is, and that she killed her attackers in Nanda Parbat. Laurel comes in to check on Thea and Oliver escorts her out to talk. He's furious that Merlyn influenced her to kill people and that Laurel didn't tell him about Nanda Parbat. She counters that he didn't tell her about bringing back Thea until he absolutely had to, because he doesn't see her as an equal. She says Sara is out of her mind right now because of a decision she made, and she's sorry about what happened to Thea because she has always loved the Queens. She just wishes Oliver cared about her family, too.
Back on Lian Yu, Oliver brings Constantine to a clearing in the jungle. Constantine says there are things on the island that bad people shouldn't have access to, but that he's on the side of the angels. He pulls up some plants, twigs and dirt and does a spell, baffling Oliver. The spell reveals a hatch in the ground, and Oliver sends Oliver down a ladder ahead of him.
At the federal building, Diggle and Lance hook up the USB device, and notice that it seems to be deleting files on individuals. They don't know whose.
In the hospital, Laurel apologizes to Thea, who says the reason Sara wants to kill her is that she's the one who killed Sara. She says that maybe if Sara kills her, Sara will be okay, but Laurel says that's not an answer.
At the federal building, Diggle notices that his brother's file is one of the ones being deleted. He frantically scrambles to stop the process, but an alarm goes off and security guards descend. Lance pistol-whips Diggle and tells the security guards that he's a cop who tracked a hacker here, and to call for backup. They leave, and Lance walks Diggle out.
In the hospital, Sara again comes to attack Thea, who tells her it's okay to kill her. Sara knocks over an IV stand and attracks Oliver and Laurel's attention during the attack, though, and Sara again leaps out the window. Oliver said Sara "wasn't there" when he looked her in the eye. He says the Pit didn't bring back her soul, but that she has a connection to Thea. Thea says they can use that.
On the island, Constantine explains that the island is a bad place that attracts bad people. He sees some writing that translates roughly to "only for the pure of heart," so he handcuffs Oliver to a post and walks in. Oliver uncuffs himself and follows John in, then saves him when his retrieval of an artifact causes a trap to be sprung.
Lance returns to Darhk to tell him he accomplished his mission, and then he asks about Andy Diggle. Darhk tells him that H.I.V.E. hired an assassin to take out Diggle. He says Diggle was competition for H.I.V.E. in Afghanistan -- that he was a crime lord and they had to take him out.
At the now-closed Verdant, Thea is hanging out waiting for Sara to show up and the rest of Team Arrow is waiting in the wings. Sara crashes through a window and attacks her, but after a brief fight with the team, Oliver uses a tranquilizer arrow on her. Laurel wants to shoot Sara, seeing that there's nothing there anymore, but Oliver stops her and instead calls Constantine for help.
Later, Constantine joins Team Arrow in the lair. He tells them that Sara needs a Restitutionum, a restoration of her soul. He gives Felicity a list of things he needs and tells the team that if things go wrong, "we'll all be too dead to care." He says he's only got enough stuff to send himself plus two people. It's Oliver and Laurel. John warns them that it won't be easy to retrieve her soul, then lights a fire in the bowl Felicity provided, chants a spell, and the three of them find themselves on "the other side." It looks like Nanda Parbat, and Sara is in the Lazarus Pit, screaming for Laurel's help. Constantine tells them to get her out, while he fights whatever comes to guard the doors, after Oliver takes out the first two League of Assassins members with his bow. Constantine has a swordfight with another LoA member while Oliver and Laurel wrestle Sara away from the Pit. Eventually, Constantine wins by casting the right spell (he tried a few) to immobilize the spirit and then stab him.
The trio all return to consciousness in the "real" world, and shortly thereafter Sara wakes up -- now calm. The Lances all hug and cry together, while Team Arrow watches and Constantine smiles.
Oliver tells Constantine he owes him one, and John says they're technically even, but Ollie says that anytime John needs anything, he'll be there.
John asks what it is that's been making the hair on the back of his neck stand up, and Oliver says that it's likely Damien Darhk. John looks concerned, and tells Oliver to watch himself. Oliver asks for advice, and John tells him to leave town. After he leaves, Thea checks in with Oliver about Nanda Parbat, but he's come around to Laurel's way of thinking that he doesn't have any room to be mad at people for keeping secrets.
In the flashback, John tells Oliver he owes him one and offers to bring him back home. He's got a boat at the shore. Oliver says Conklin (the other soldier) suspects him too much already so he can't go back empty handed. Constantine breaks a valuable-looking orb off the top of the staff they've just recovered, saying the true power is in the gremoire -- a spell book inscribed on the staff. He says people like Reiter always get attracted to the sparkly bits, but then he uses the staff to remove a tattoo from his arm while reciting a spel. He tells Oliver to lift up his shirt and holds his hand to Ollie's stomach, where the tattoo reappears. Oliver tells Constantine to punch him to make the escape look convincing, and Constantine does.
Cut to the current day, when Oliver is about to step on stage for an interview. Alex is there, but so is Laurel. Oliver tells him that he's not going to distance himself from Laurel, and Alex says he guesses he gets paid either way. Thea tells Oliver she's proud of him.
Laurel thanks Oliver, and tells him that Sara is resting. He says she was right that he hasn't always been the best friend, but that he wants to start to be better. The two hug.
Lance knocks on Diggle's door, bringing a hard copy of a classified file on Andrew. He says "You don't have to read this. You can remember your brother how you knew him," and gives the file to Diggle, who's incredulous, and crestfallen, but glad to know the truth.
At Palmer Tech, Curtis has drank a huge number of energy drinks and has cleaned up Ray's message. It tells her that he's alive, and he's in trouble.