Helena is back to seek vengeance, but Oliver still has feeling toward her. The Arrow must stop and kill her, but at what costs? Now that several of his closest friends know about his true identity, no one is safe.

After a major fire, Oliver decides it's time to eliminate real estate developer and slumlord John Nicol, another person on his father's list. He's beaten to the punch when another vigilante, The Savior, who kidnaps Nicol and ultimately executes him - broadcasting the whole thing over the Internet. The new vigilante is identified as a man whose wife was killed in a bodega robbery in the Glades district. When he kidnaps Thea's new boyfriend, Roy Harper, Oliver decides to stop him. Meanwhile, Laurel is upset to find that her father has come around to her mother's belief that her sister may still be alive. In a flashback to his days on the island, Oliver learns why Yao Fei refused to leave.

As a new enemy emerges seven months after Slade's attack upon Starling City, Oliver battles with the help of his teammate Roy. However, with the Arrow's presence elsewhere someone he had loved dearly is hurt.

Nyssa and Oliver join forces to go after the Dark Archer.

Oliver must stop an Arrow-obsessed serial killer, Carrie Cutter, who is convinced that The Arrow is her one true love and will stop at nothing to get his attention. Unfortunately, her way of getting his attention is to kill people. Meanwhile, Ray asks Felicity to be his date for a work dinner with important clients. Thea auditions new DJs for Verdant and meets Chase, a brash DJ with whom she immediately clashes.

Oliver struggles to adjust to the changes that have taken place within Team Arrow; Laurel ignores Oliver and pursues Vertigo - who injects her with the drug; Thea receives a surprise visitor.

During an attack on the mayor's office, Ray is critically injured. Felicity is pleasantly surprised when her mother, Donna Smoak, shows up at the hospital to offer her support. With the SCPD out in full force looking for the assailant, Oliver and his team work hard to stay one step ahead of the police to find the man responsible. However, things come to a head when Ra's al Ghul kidnaps Captain Lance.

Oliver and Thea are concerned when a family friend plans to run for mayor; Thea starts to exhibit side effects from the Lazarus Pit; Felicity asks an employee for help with a business decision.