"Deathstroke Returns" starts off with Dinah walking out of the police department talking with her colleagues when a sniper begins to open fire. Dinah — and everyone else — dive out of the way. They're all safe.
Rene calls Oliver so the two can talk about the situation. Oliver orders Rene to find out the identity of the shooter and he hangs up — Slade Wilson is with him at home.
Slade begins telling Oliver about his son — he joined an Australian intelligence outfit and got into trouble. He got put in jail for life. Slade asks for Oliver's help — but not as the Green Arrow. Rather, Slade wants him to act as a diplomat.
We see a flashback of Slade with his son, they're camping and his son mentions that he's upset because Slade always manages to leave.
Felicity and Curtis are going over security footage when they recognize the shooter was Vigilante, and he was apparently a city councilwoman.
While investigating the shooter's nest, Dinah and Diggle bump into Special Agent Watson, the FBI agent investigating Oliver. After a confrontation with her, Diggle leaves the scene.
Oliver is talking with Felicity with his situation with Slade. Felicity reminds Oliver that he wouldn't be suiting up as the Green Arrow and Oliver keeps reiterating that he'll keep beating himself up because he promised William he'd stay away from that stuff.
Slade's outside his vehicle waiting for Oliver to show up, who does a few seconds late and they head to find Slade's son.
Dinah is staking out Councilwoman Pollard when she notices Vigilante working his way up the fire escape to her apartment. She leaves her vehicle and approaches him and after using her powers to knock him back, Vigilante takes off his mask to reveal his identity — Vincent Sobel.
The team gathers at HQ and Dinah tells the rest of the team it was Vincent, her old partner — and boyfriend — who she witnessed being shot in the head.
Felicity's phone rings and it's Special Agent Watson — she wants to meet.
Oliver and Slade have arrived in Kasnia. They're meeting with one of Slade's old friends, who hands over a folder with intelligence. The friend tells Slade that his son was snooping around some mercenaries when he was arrested.
Felicity is meeting with Special Agent Watson, who asks her if she's willing to testify under oath to agreeing she was Oliver's alilbi on the nights Green Arrow was active. Felicity gets a text from Curtis that he found more information of Dinah's ex partner.
Oliver and Slade are hatching out a plan to pick up Slade's son. Slade gives Oliver a case full of money and airplane tickets to London, he orders Oliver to not tell his son he helped out. Slade is afraid of his son looking down upon him for being Deathstroke. Oliver tries to persuade him otherwise but Slade isn't biting.
We see another flashback — Slade and his son are sitting around a campfire. His son keeps asking questions, which Slade doesn't answer truthfully and his son gets up to walk away from the fire.
Team Arrow gathers at the last known location of Sobel to find more information on the presumed-dead ex-cop.
Oliver meets with the diplomat who can release Slade's son from prison. We see Oliver soon return to Slade with the briefcase of money and Slade knows something's amiss. Oliver says that Slade's son was killed in a prison yard brawl.
A distraught Slade begins mourning his son — he expresses his regret of not going to the prison with Oliver.
We see another flashback with Slade and his son Joe — Slade's apparently scoping out one of the other families at the campground.
Dinah is training against a dummy when Diggle walks in to talk to her about the return of the presumed-dead boyfriend. Rene walks in and says he has two problems: first, Councilwoman Pollard has scheduled an interview about her anti-vigilante referendum and two, he has been subpoenaed.
Oliver and Slade go back to the prison to see Joe's body. When they approach the warden, the warden reveals he lied to Oliver earlier. Joe didn't die in a prison yard brawl, rather he was taken by the gang he was covertly investigating.
Dinah has called
Back is Kasnia, Slade is suiting up in his Deathstroke uniform to go hunt down the Jackals that took his son. Oliver tries talking Slade from going on the adventure and then faints — he's been drugged by Slade so that he doesn't compromise the mission.
We see another flashback at the campsite where Slade and Joe are eating. Slade notices the man he's been observing walk by. He sneaks away to put on his Deathstroke suit to approach the man. After a struggle, Slade slits the throat of the man.
Diggle shows up to the TV station where Dinah is at and they start talking about Vincent. Dinah promises that nothing remains of the main she used to love. The interview starts and we see Vigilante approaching the set on a catwalk near the ceiling — he has a gun drawn.
Councilwoman Pollard is in the middle of the interview when the power is cut out. She runs from the set and is chased down by Vigilante. Dinah appears and distracts Vigilante so that Pollard can get away.
A nervous cop shows up and shoots Vigilante in the head and he falls to the ground. Vincent takes his helmet off and the bullet has been crushed against his forehead — he's bulletproof.
Dinah and Vincent talk about being affected by Dark Matter and when police sirens rage on in the distance, Dinah lets Vincent walk from the scene so he doesn't get arrested.
Dinah radios into Team Arrow and tells them Vigilante got away.
Oliver wakes up in Kasnia and sees a note left by Slade that tells him to go home. His phone rings and William's calling — he asks when he's coming home. Williams says he wishes his dad could have helped Slade find his son and Oliver agrees.
Slade's gotten to the Jackals' hangout and starts wreaking havoc. He kills nearly everyone in his way but is soon overpowered. While surrounded, we see the man Slade got the intel from earlier — he's the ringleader behind the group.
We get another flashback of Slade and his son Joe, they're leaving the campground.
Dinah is packing up from the scene when she's approached by Special Agent Watson. Watson tells Dinah that she heard Pollard was saved by the new Black Canary. Watson says that when the lights went off, Dinah was nowhere to be seen, hinting that she thinks Dinah is the Black Canary.
Dinah turns around to leave in her car and she finds a small box on her dashboard — it's a paper rose, a gift from Vincent.
Oliver shows up to the place where Slade is being held captive now. Slade agrees to join the Jackals so long as they let Joe go. The friend reveals that they can't let Joe go, he's their boss.
Joe walks into the light and greets his father, saying it's been a long time since they've talked.