“The Return” opens with Oliver and Thea training on the island of Lian Yu. Oliver is surprised with Thea’s skill level, wondering what Malcolm exactly trained her in Corto Maltese. Later that night, the siblings discuss Oliver’s first time on the Island over five years ago. She asks Oliver if he ever wondered if he’d return to Starling City while marooned.
The question jogs Oliver’s memory—and the show—to the past. Oliver, Maseo, and ARGUS are Starling City looking the Omega Virus. Amanda Waller thinks an auction will occur through an old Queen family partner named Kang, and needs Oliver’s intel on him to bust the auction. However, Oliver can’t let anyone know that he’s back in his hometown, otherwise Waller kill him. Maseo later puts a tracker on Kang’s car. As they follow him, Maseo and Oliver see Thea Queen leave Queen Consolidated’s building.
Back in the present-day Starling City, Laurel finds Captain Lance drinking alone in a bar, mourning Sarah’s death. When the bar tender cuts Lance off, Laurel gives him a ride home. Over on the island, Oliver wakes from a bad dream. Thea comforts him, but asks Oliver never told her about Sara’s death. Oliver discusses her connection to Slade while on Lian Yu, and then excuses himself to take a walk.
That walk leads him right to Slade’s ARGUS prison beneath the island’s surface. Oliver walks to Slade’s cell, but find’s that Slade isn’t in it. Deathstroke has escaped, and Oliver rushes out of the prison to find him. He finds Thea, and says that they have to leave the island immediately. Oliver receives a phone call from Malcolm Merlyn, who reveals that he freed Slade from his cell. With Deathstroke loose on the island, he hopes that Oliver will rediscover his killer instinct, and thus be more ready for Ra’s al Ghul.
Back in the past, Oliver follows Thea as she visits the empty graves of Oliver and his father. Oliver watches Thea buys drugs from a dealer who approaches her. The deal is busted however, when Tommy Merlyn shows up and warns Thea from growing up too fast. Tommy scorns Thea for her drug use and party-going, warning her not to go to his birthday party that night.
In the present, Oliver uncovers an old weapons cache on the island. He hands Thea a gun, but is suddenly ambushed by Slade. Sade knocks him out, and tells Thea that it’s nice to see her again. He takes Oliver and Thea to his former cell. When Oliver wakes, he says that he has no desire to kill either of them. He says that he’s going to let the two of them rot in his cell, like Oliver left him. Thea calls Slade “sick.” But Slade counters by telling Thea that Oliver is keeping more secrets about Sarah from her. With that question dangling, he leaves.
In the past, Oliver breaks into Queen Consolidated. He hacks into the company’s computer directory to find the Omega auction’s details in Kang’s files. As Oliver downloads the files, Felicity Smoak enters the room. Oliver ducks and hides as Felicity approaches the computer. Oliver leaves undetected, with the info that the auction will go down that night. Waller wants to know where Oliver is going next. Oliver sneaks to Tommy Merlyn’s birthday party across town. In disguise, Oliver sees Tommy flirt with Laurel. He also see’s Thea crash the party. Tommy tells her to leave, but she ignores him. She then meets her drug dealer, who slips her something that will keep her “awake.”
Oliver ambushes the drug dealer and warns him to leave Thea alone. The dealer recognizes Oliver and tries stabbing him, but Oliver grabs the knife and kills him first.
On present-day Lian Yu, Oliver and Thea work on an escape plan. Thea asks Oliver what he’s still hiding about Sarah. But Oliver dodges with question with an idea. He realizes that the cell’s bars are only narrow enough to contain a grown man’s arms, but not a smaller female’s like Thea’s. He then dislocates Thea shoulder (with her permission) so she can reach the cell’s release button just a few feet away. The cell opens, and the two escape to reach Slade before he reaches their plane.
Back at Tommy’s party, the police arrive to investigate the dead drug dealer’s body. Leading the police is a drunk Captain Lance, who’s a much meaner version of himself. He finds Laurel at the party, and starts criticizing her for hanging around fat cats and playboys. When Oliver rendezvous with Maseo, Maseo asks Oliver what he was thinking. Maseo says he can’t interact with his family, and if he really wants to help them, he’ll focus on stopping the Omega Virus auction. Oliver ignores him, and leaves to be his loved ones.
In the present, Oliver and Thea race to Slade. They hit a snag, however, when they trip one of Oliver’s booby traps. As they rest, Thea asks Oliver again what secret about Sarah he’s holding from her. Oliver then tells Thea that it was she, who under Malcolm’s drugs, killed Sarah. Thea has a meltdown, but Slade interrupts with an ambush. He puts a gun to Thea’s head, but she disarms him. Oliver then tackles Slade, and the two duke it out in the woods. Thea joins the fray, and it’s an all-out brawl. The two get the better of Slade, and Thea draws the gun on him. She resists the temptation, however. Thea and Oliver lock Slade back in his cell. Sade warns Oliver that Malcolm has corrupted Thea, and that she is truly lost.
In the past, Oliver returns to Queen manor. He sits down in the family living room and watches a video file left for him by his father. In the video, Oliver’s father tells him that if Oliver is watching this, he is dead. But the posthumous video asks Oliver to save Starling City from the corrupt men who rule it, and right his past wrongs. Oliver knows that he must put his emotional needs aside, and fight for his city instead. He leaves for the auction.
Across town the Omega auction takes place, with Maseo watching. But Maseo is discovered, and is about to be killed, until Oliver saves him at the last minute. The auction turns into riot, but Oliver and Maseo manage to subdue the auction’s criminals and recover the Virus.
Oliver thinks their mission is over, but Waller corrects him. Then, a military general enters the room and says that he must tell Oliver some bad news back in China. The general assures, however that once Oliver is debriefed, the general will let him go wherever he pleases. Across town, Tommy runs into Laurel on the streets. He then asks her out to dinner, which she hesitantly accepts.
Back in the present, Laurel finds her father at Sarah’s grave. He asks Laurel how she could break their special bond by holding such a secret from him. He says he doesn’t know how he’ll live with the betrayal, and leaves Laurel to herself.
Across town, Thea and Oliver return to their apartment. Thea insists that she’s fine, but Oliver warns Thea from telling anyone—especially Laurel— that she knows she is Sara’s murderer. Malcolm then shows up. Thea bombards Malcolm and asks how he could let her kill Sara. Malcolm tries using Ra’s as an excuse, but Thea won’t listen. She says she’ll continue working with Malcolm to stop Ra’s, explaining that she’ll be his partner, ally, and soldier. But, she’ll never be his daughter.