With his nightclub set to open and a new romance brewing with McKenna, Oliver is as happy as he's been since returning to Starling City. But when Oliver's ex, The Huntress, suddenly returns to town, she threatens to destroy everything and everyone he cares about. Meanwhile, Laurel and her father struggle with the return of Dinah Lance who claims she has proof Sara is still alive. Thea gets Roy Harper a job at Oliver's club, but he's not too inclined to stop his life of crime. Oliver and Tommy are thrilled they were able to get Steve Aoki to play at the opening of their new nightclub, Verdant.

Finding it difficult to mend fences with Tommy and Diggle, Oliver instead focuses on crossing another name off the list. While digging through a crooked accountant's laptop, Felicity discovers a transaction that could help Oliver find Walter. To reconfirm the lead, Oliver gambles that Felicity can be counted on in the field for the first time. In a flashback, Malcolm reveals to Robert Queen and Frank Chen painful details surrounding his wife's murder, and how that shaped his plans for the Glades. Meanwhile, Tommy stuns Laurel with the truth.

Oliver puts Sara Lance up at the manor and soon discovers that she doesn't want to contact her family... both because she would put them in danger, and because she become a killer since the last time they saw her. Meanwhile, the League of Assassins send men to bring Sara back, alive or dead. And Oliver discovers that Laurel will be sitting second chair for his mother's trial.

A bomber nicknamed Shrapnel has set his sights on Sebastian Blood, and Oliver dons his mask to protect his newfound ally. Meanwhile, Laurel investigates Sebastian's aunt who is locked up in a mental institution, and Thea learns about Roy's newfound superstrength.

As Laurel continues to unravel, Oliver and Lance try to convince Sara to stay in Starling City and finally reunite with Laurel and Dinah. However, Sara’s fellow League of Assassins member, Nyssa, comes to bring Sara back to the fold, but when Sara refuses, Nyssa kidnaps Dinah. Realizing she’s putting her family in danger by staying in town, Sara considers re-joining the league.

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.

A mysterious archer known as Komodo appears in town and begins skewering businessmen. Meanwhile, Oliver worries about Thea, which forces Roy to tell him the truth about why she left town; and Ray Palmer pursues Felicity. In a flashback, Oliver is assigned his first kill and the target is his best friend, Tommy.

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.

Vertigo causes Laurel to hallucinate an epic fight that pits her Black Canary against her sister Sara. Meanwhile, Chase surprises Thea and Roy warns Thea to stay away from Malcolm.