When a new gang, the Ghosts, hit the newly renamed Star City, Diggle, Thea, and Laurel find themselves in over their heads. Laurel and Thea interrupt Oliver and Felicity's quiet suburban lifestyle to ask them to come back and help.
Moira's friend Jessica Danforth decides to run for mayor of Star City. While Team Arrow tries to protect her, Oliver realizes that the Lazarus Pit is taking its toll on Thea. In the past, Oliver meets Baron Blitzkrieg, who offers Oliver a job.
Damian brings in a metahuman, Double Down, to take care of Green Arrow. Meanwhile, Diggle and Green Arrow continue working separately because of their past. And Laurel and Thea travel to Nanda Parbat: Thea to find a cure for her bloodlust, and Laurel to resurrect her sister.
Team Arrow discover that a gang of crooked cops is robbing drug dealers and selling their product. Oliver turns to Quentin for help, but soon learns that he is working with Damian. Meanwhile, Laurel brings Sara to Star City and reunites her with Quentin, but his reaction isn't what she had hoped.
Sara goes on a killing spree, and Oliver realizes that when she was brought back, her soul didn't come back with her. As Sara stalks the person who killed her, Oliver turns to an old friend from Lian Yu for help: the sorcerer John Constantine.
Felicity convinces Oliver to launch a desperate rescue attempt to recover a miniaturized Ray from Damien's captivity. Meanwhile, Sara finds herself giving in to the bloodlust of the Lazarus Pit, and Oliver thinks it's a good idea if Felicity takes some time off with her mother Donna.
While Green Arrow and his team set out to recover Andy from Damien's forces, Ray tells Felicity that he's not sure what he's going to do with his future. Meanwhile, Thea receives a visit from Malcolm and gives in to her bloodlust in front of a shocked Alex.
The two teams of superheroes take refuge at a farmhouse while Carter trains Kendra in her newfound powers. However, when things go horribly wrong, Flash timejumps and tries to prevent catastrophe from happening again.
Oliver goes public with Damien and HIVE, but is unprepared for the consequences. Meanwhile, Malcolm arrives in Star City to help his daughter, and Felicity discovers that Oliver was going to propose to her.
After Damien's attack on someone close to him, Oliver goes on a bloody manhunt trying to find the HIVE leader. However, Anarky returns to Star City with his own plan for revenge. Meanwhile, Thea confronts her blood lust while Diggle tries to reach his brother.
Shadowspire, a rogue military organization with ties to Diggle's time in Afghanistan, launch an attack on the A.R.G.U.S. agents that exposed them years before. Diggle has no choice but to rely on Andy for help. Meanwhile, Felicity confronts a specter from her past while dealing with her new role in Team Arrow.
Roy returns to Star City... working for a new villain, the Calculator, a genius computer hacker who plans to bring the city to its knees. Meanwhile, Thea's condition worsens, and in the past, Oliver takes the first step to leaving his darkness behind.
Oliver refuses to kill Malcolm in return for Thea's cure, and Malcolm refuses to surrender rulership of the League to save his daughter. Civil war tears through Star City as the two factions fight it out. Meanwhile, Felicity discovers that the Calculator is her father and tests him to see if he can be trusted.
While Oliver preps for a debate, Quentin tries to shield his new girlfriend Donna from the truth that he was working with HIVE. Both men find themselves with larger problems with Damien unleashes a demolition expert on Star City to guarantee his wife's rise to power.
Damien demands that Oliver resign as a mayoral candidate, or he will kill William. In response, Oliver brings in a superhuman ally, Vixen, to help him track down his son.
Cupid returns to Star City and vows to prove to everyone that love is death. Meanwhile, Oliver and Felicity deal with the aftermath of their break-up. In the past, Oliver discovers that Reiter plans to use the lives of the slaves to power a mystical idol hidden deep beneath the island.
After hacking her way out of prison, Brie Larvan makes her way to Palmer Tech to steal Felicity's spinal implant. The villain uses her robot bees to cut off all access to the outside world, trapping Felicity, Thea, and Donna inside. Meanwhile, Malcolm delivers a message to Damien in prison.
Team Arrow are forced to trust Andy to help them track down the idol after Malcolm steals it for Damien. However, Oliver and Diggle disagree on whether they can trust Andy, threatening to tear the team apart.
Star City reels under the news that ADA Laurel Lance is dead. However, a new Black Canary emerges... and will kill anyone who she holds responsible for Damian's crimes.
Oliver calls in a favor with Constantine and goes to meet with an immortal shaman who can teach him how to fight Damien's dark magic. Meanwhile, Thea takes a break with Alex, while Diggle visits Lyla and Sara.
The team is forced to find Noah Kuttler--Felicity's father--to disarm the nuclear missiles that Damien has taken control of. However, Damien has sent two of his men to kill Noah and prevent his interference. Meanwhile, Anarky finds Damien's shelter and tries to destroy it.
While Green Arrow and Spartan try to rescue Thea from Tevat Noah, Felicity, Noah, and Curtis try to shut down Rubicon for good. However, Damien has a hacker of his own... and Anarky has his own plans to destroy everything.
With the world counting down to nuclear armageddon, Felicity and Curtis must find a way to stop the missiles. Meanwhile, Oliver tries to convince the citizens of Star City that they are stronger together than apart.