After Detective Lance arrests Oliver for murder, Oliver tells Moira the only lawyer he'll allow to represent him is Laurel. Laurel takes the case which puts her at odds with her father. Oliver offers to take a polygraph in front Detective Lance but things get tense when Lance asks him if anyone else was on the island with him. Oliver flashes back to when he got his first scar, courtesy of Deathstroke.

Oliver’s confidence is shaken after being beaten by the Dark Archer and he takes a break from being Arrow. However, when Laurel calls Arrow for help investigating a firefighter’s suspicious death, he reluctantly agrees but his hesitance while fighting almost costs him his life. Meanwhile, Tommy throws a benefit for the firefighters and Thea tries to lift Moira out of her depressive state.

Thea is in trouble with the police after she gets caught using a drug called "Vertigo." Oliver thinks the only way to keep her out of jail is to find the dealer, a man who goes by the name of "The Count". Oliver turns to McKenna Hall, an old flame and current Vice cop, for help. Meanwhile, Laurel steps in to defend Thea, and Felicity gives Oliver some disturbing news about Moira.

Deadshot returns to Starling City after taking down a U.S. Ambassador and six others overseas. By keeping tabs on A.R.G.U.S.'s manhunt for the assassin, Oliver, Diggle, and Felicity learn that a sting operation is underway to capture Deadshot - alive. Diggle is determined to see his brother's killer dead, with or without Ollie's help. Meanwhile, Laurel takes drastic steps to protect a young witness, exacerbating friction between Tommy and Oliver. Later, Roy Harperunconventionally pursues all leads to find his new hero, but runs afoul of Detective Lance. Back on the island, Oliver recalls how Shado helped him incrementally gain confidence with a bow and hit the target for the first time.

Thieves hijack medical supplies sent to Glades Memorial. Oliver gets into a heated battle with China White and her new partner, the Bronze Tiger, over the supplies. Meanwhile, Laurel makes plans to catch the Arrow; and Thea give Roy an ultimatum.

A.R.G.U.S. abducts Diggle and asks him to help recover Lyla from a Russian prison. Oliver and Felicity insist on going along to help and Isabel tags along. Meanwhile, Jean Loring advises Thea that her dating Roy is hurting Moira's chance of getting an acquittal.

In the present, Slade visits Oliver and makes his intentions clear. Five years earlier, Slade, Sara, and Oliver launch their assault on the Amazo, but things go wrong when Slade learns that Oliver was responsible for Shado's death.

Oliver rallies his team as Slade's soldiers attack the city. Felicity gets a call from S.T.A.R. Labs with game-changing news and Thea comes face-to-face with her father.

Felicity's past as a crusading hacker is revealed when someone uses a super virus that she designed to bring Starling City to a standstill. Meanwhile, Oliver and Thea work on their new relationship, and Felicity's mother pays a visit.

Brick takes three city aldermen hostage and demands that Mayor Castle turn the Glades over to him in return for their safe return. Meanwhile, Felicity turns to Ray for help when she needs a helicopter, and Laurel realizes that she may be in over her head with her new crime fighting carer.

Laurel must deal with the repercussions of taking Sara to Nanda Parbat. Meanwhile, Oliver asks Captain Lance for a favor and while he's not surprised at the response, he is surprised at what he finds out next.

After the city is attacked again, Oliver makes a bold move against HIVE. Malcolm checks in on Thea and leaves her with a warning. Things take a horrible turn when Damien Darhk retaliates in a brutal manner at Oliver’s mayoral holiday party.

Oliver receives an offer from Nyssa that is hard to refuse. Meanwhile, Thea continues to battle the blood lust, Malcolm steps in to help his daughter, and Laurel has a heart to heart talk with Nyssa.

Brie Larvan breaks out of jail and turns up at Palmer Tech threatening to kill everyone unless she gets the bio-chip that is implanted in Felicity’s spine. When Oliver realizes that Felicity, Thea and Donna are trapped in Palmer Tech with everyone else, he looks to a surprising ally to help Team Arrow save the day.

The Green Arrow is forced to face a powerful new drug dealer when Wild Dog goes off on his own.

When the bodies of two criminals are dropped at SCPD, Oliver realizes there is a new Vigilante in Star City. The team is split about whether they should stop someone who is helping keep the city safe. Diggle is frustrated with his new situation and Thea fights for Lance who confesses a shocking secret. Meanwhile, in the flashbacks, Oliver finally sits down with Konstantin Kovar.

Worried that Prometheus is right and he is truly a killer at heart, Oliver looks for any ray of hope and finds it in what seems to be the miraculous return of Laurel Lance. However Felicity, still reeling from Detective Malone's murder, is bent on revenge - she wants to stop Prometheus at any cost. While in prison, Diggle fights for his life.

Oliver faces his biggest challenge yet as mayor. Felicity continues down her dark path with Helix. After Vigilante attacks Oliver while he's acting as the mayor, Diggle leads the team in a mission to stop Vigilante once and for all.

Slade returns and asks Oliver for help in tracking down his son. When they learn Joe has been taken hostage by mercenaries, their mission to save him gets complicated by a terrible revelation that could shatter Slade's hopes of reunion forever. Meanwhile, Vigilante reappears in Star City.

Despite losing half his team, Oliver remains confident that he, Felicity and Diggle can stop Cayden James and Black Siren. However, when he discovers one of Cayden’s secrets, he decides to team up with an unlikely ally. Meanwhile, Dinah spends time with Vince.

Nyssa Al Ghul returns to Star City to warn Thea that a group of renegade League of Assassins members are planning to attack her. This group, led by Athena, is intent on finding a mysterious box that Malcolm left behind and will stop at nothing to get it. Nyssa helps Oliver come to a life-changing realization.

Diaz targets Team Arrow and their loved ones. Oliver struggles with Felicity putting herself in danger when she gets the chance to stop Diaz for good.