With crime at an all time low, Oliver decides to take a break and asks Felicity on a date. However, they're interrupted when a new drug dealer take the name of Count Vertigo and targets the Arrow for death. Meanwhile, Diggle becomes an expectant father and a scientist tries to acquire Queen Consolidated before Oliver can retake his family's business.
Oliver and his team try to find the archer who killed Sara, and discover that a hitman calling himself Komodo had connections to their friends past with the League of Assassins. Meanwhile, Ray continues trying to hire Felicity, and Roy debates whether to tell Oliver why Thea left Starling City.
Felicity tracks Thea to the island of Corto Maltese, and Oliver, Roy, and Diggle got here to bring her back. Meanwhile, Lyla asks Diggle to look into the disappearance of ARGUS agent Mark Shaw, and Laurel looks for an outlet for her frustrations.
Nyssa believes that Malcolm killed Sara and goes after him to avenger her lover's murder. Oliver discovers that he has no choice but to stop her, despite Laurel insisting that he avenger her sister's death. Meanwhile, Thea returns to Starling City and settles in... until Nyssa discovers that she's Malcolm's daughter.
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.
A killer is murdering his victims and attempting to frame Ted Grant. The Arrow finally comes to his aid after Laurel protests her trainer's innocence. Meanwhile, Roy goes to Felicity for help determining if he killed someone under the influence of Mirakuru.
The Arrow is stalked by an ex-police officer who he rescued during the Mirakuru siege and has become dangerously obsessed with the hero. Meanwhile, Ray asks Felicity to accompany him to a business dinner, and Thea is forced to hire a new DJ for Verdant.
As Barry, Caitlin, and Cisco arrive in Starling City to help with the investigation into Sara's murder, former Suicide Squad member Digger Harkness goes after Lyla. The Arrow and his team need all the help that they can get to stop the boomerang-wielding killer, particularly when he sets five bombs in the city to cover his escape. In the past, Amanda Waller teaches Oliver how to make the hard choices... whether he wants to or not.
Ra's al Ghul sends Nyssa and her lieutenant to Starling City to inform Oliver that the League will kill 50 people a day until Sara's murderer is turned over to them. With time running out, Oliver finally identifies the killer... and realizes that he can never turn them over for execution. Meanwhile, Ray shows Felicity his new project.
With Oliver gone, Diggle, Arsenal, and Felicity have their hands full dealing with a new crime lord: Brick. Meanwhile, Ray prepares his battle armor, and in Tibet, a mysterious figure finds Oliver's body.
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.
Still operating without Oliver and desperate to stop Brick, Team Arrow is forced to consider Malcolm's offer to help shut Brick down as Malcolm has a personal score to settle with the felon. Roy and Laurel point out that the team could use some help to save the innocents of The Glades, but Felicity is adamantly against it. They look to Diggle to make the final decision. Meanwhile, the flashbacks chronicle Malcolm's descent from kind-hearted father and husband to cold-blooded killer after the murder of his wife.
Source: The CW
Oliver is thrown by the changes within Team Arrow. He's used to calling the shots but sees that the team has evolved in his absence and tensions quickly escalate in the lair. Oliver is furious that Laurel has been going out as the Black Canary and tells her to stop risking her life, but when Vertigo hits the streets again, Laurel goes against Oliver's wishes and tracks down Vertigo who hits her with a full dose of the drug. Laurel's biggest fears revolve around her sister Sara so the Vertigo causes her to hallucinate an epic fight between Canary and Black Canary. Meanwhile, Chase surprises Thea (Willa Holland), and Roy warns Thea to stay away from Malcolm.
Source: The CW