• Stephen Amell
• David Ramsey
• Emily Bett Rickards
• Echo Kellum
• Rick Gonzalez
• Juliana Harkavy
• Colton Haynes
• Kirk Acevedo
• Sea Shimooka
• Katie Cassidy

Five months after being exposed as Green Arrow and into his life sentence,Oliver Queen tries to maintain a low profile in Slabside Maximum Security Prison in hopes of getting a reduced sentence, an effort which is complicated whenDanny "Brick" Brickwell tries to coerce Oliver into helping him and by him being stalked byRicardo Diaz's associates. Meanwhile,Felicity Smoak andWilliam Clayton try to cope with witness protection whileJohn Diggle andA.R.G.U.S. continue hunting the fugitive Diaz. Back inStar City, a new vigilante archer appears on the scene, targeting criminals on their list while also helping the city's poor. After being saved from a group of criminals,Rene Ramirez decides to trust the vigilante, despite not knowing who is under the hood. The rest of Team Arrow do not trust the archer andDinah Drake is determined to make an arrest. Because the archer's tactics, skills, and appearance parallel Oliver's suited persona, the media dubs the vigilante as the new Green Arrow. After being discovered by Diaz, Felicity leaves witness protection to help capture him.

The Longbow Hunters arrive in Star City and the team works together with A.R.G.U.S. to try and stop them from stealing a weapon with incredible destructive capabilities. Felicity and Diggle clash over their priorities in dealing with Diaz, leading Felicity to strike a deal withAgent Watson. Meanwhile,Laurel Lance and Dinah are forced to put their feud aside and work together, while Oliver tries to get rid of a prison guard in exchange for info on Diaz from Brick.

In prison, Oliver is tortured both psychologically and by means of drugs and electrical devices, in order to "reprogram" his brain. In Star City, Dinah arrests Rene when she learns that he is providing support to the new Green Arrow but, when the vigilante savesZoe Ramirez's life, she has a change of heart. Working together, Dinah, Rene, and the vigilante are able to capture a group of arsonists plaguing Star City. Elsewhere, Felicity enlists the help of Laurel to torture the Silencer for information on Diaz, but to no avail. Felicity allows her to escape in the hope that she will lead them to Diaz, having planted a bug in her belt.

Diaz slaughters the Bratva and torturesAnatoly Knyazev in order to get in contact with one of his former KGB associates. Team Arrow rescues Anatoly and discovers that Diaz plans to level Star City with aerial explosives obtained from the associate. Team Arrow foils the plan and finally captures Diaz with help from the new Green Arrow. Meanwhile, in Slabside,Stanley Dover is accused of murdering a guard, but proclaims his innocence. Oliver finds the knife used in the attack, which belonged to Brick's associateBen Turner. Released from solitary confinement, Stanley thanks Oliver, but inadvertently reveals knowing that the knife belonged to Turner, information he could not have gotten in solitary. At Star City Police Department (SCPD), Laurel orchestrates a deal which will see Oliver walk out of prison in exchange for helping the FBI with their case against Diaz.

Now free from prison, Oliver tries to readjust to outside life. When a murder occurs at a party honoring Oliver, the new Green Arrow is suspected and Oliver, Dinah, and Rene set out to prove the vigilante's innocence. Meanwhile, Oliver and Felicity struggle to adjust to the changes Oliver's incarceration inflicted upon their lives and relationship. After she helps Oliver arrestMax Fuller for orchestrating Frank Cassady's murders of Sam Hutchinson and Clayton Ford, Dinah authorizes Oliver to work with the SCPD as a special deputy in order to avoid the anti-vigilante law, much to the annoyance of MayorEmily Pollard. Diggle and Lyla connect the Dante painting and the Zürich finances to an individual who has a transaction history with multiple terrorist cells, including both the Longbow Hunters and Diaz. Unbeknownst to Team Arrow, they pay Diaz a visit in prison to request his assistance. Meanwhile, the new Green Arrow is revealed asRobert Queen's daughter.

Oliver,Barry Allen, andKara Danvers head toGotham City to findJohn Deegan, but are quickly arrested. However, they are bailed out byKate Kane, who tells them Deegan can be found atArkham Asylum. With some assistance from Oliver and Barry's teams, they break in to confront Deegan and retrieve the book he used to rewrite reality, only for the doctor to escape by causing a mass breakout. While trying to contain it, Batwoman shows up to help them before telling them to leave Gotham. Returning to A.R.G.U.S., the heroes attempt to unlock the book when theFlash of Earth-90 breaches through to them and warns them of theMonitor. Oliver, Barry, Kara, and Earth-90's Flash go to confront the Monitor, but the omnipotent being escapes and returns the book to Deegan, who changes reality once more. This time, Oliver and Barry wake up as wanted criminals and are forced to contend with both the police and a black-suitedSuperman.

Oliver discovers blood belonging to the new Green Arrow and Felicity determines that it belongs to a woman namedEmiko Queen, Oliver's father's illegitimate daughter and thus his paternal half-sister. Oliver goes through his father's belongings and discovers thathis mother knew about Emiko and her motherKazumi Adachi. After being injured, Emiko goes to Rene for help and reveals that she seeks to avenge her mother's murder in the Glades. Emiko visits her father's grave, where she is confronted by Oliver. Meanwhile, in order to be able to work without A.R.G.U.S. oversight, Diggle and Lyla restore theSuicide Squad as the Ghost Initiative, recruiting Diaz as its first member and implanting an explosive into his neck to ensure his compliance in tracking down terrorist financierDante.

Oliver allows a camera crew to follow himself and others associated with Team Arrow around and film a documentary titledThe Hood and the Rise of Vigilantes. A new vigilante, named Chimera by Curtis, begins attacking vigilantes in Star City, includingRagman,Huntress, and the new Green Arrow. William returns from witness protection and tells Felicity he was expelled from school, while Oliver debates Mayor Pollard about vigilantism but is interrupted by Chimera. During the attack, Dinah saves Pollard using her Canary Cry, revealing her identity as the Black Canary. When Team Arrow arrives and helps Oliver capture Chimera, Pollard arrests them, prompting Oliver and Dinah to turn themselves in and resulting in Pollard deputizing Team Arrow as part of the SCPD.

Members of Team Arrow receive threatening notes and discover a similar note at the murder scene of a councilman who previously worked with Ricardo Diaz. Tracking a drug used to immobilize the victim, they discover the hiding place of the "Star City Slayer," who is revealed as Stanley. He slits Dinah's throat, but Curtis cauterizes the wound, saving her life. Stanley confronts Oliver, Felicity, and William at their apartment, claiming to be the only one who truly understands Oliver. While Felicity distracts Stanley, Oliver subdues him and he is sent back to Slabside. William, wanting a normal life, chooses to live with his grandparents. Curtis accepts a job in Washington, D.C. and leaves Star City, signing sole ownership of their Helix company over to Felicity. Meanwhile, a medical checkup discovers something important about Felicity.

Felicity and Laurel continue growing closer, with Felicity revealing to her that she is pregnant with Oliver's child. John and Lyla successfully locate Dante with the Ghost Initiative, identifying A.R.G.U.S. DirectorBell as the mole. During the operation to catch Dante, Diaz betrays the team to warn him and he escapes, killing Bell and potential clientQuraci Princess Noor in the process. Diaz is taken back to Slabside, where an unseen assailant lights him on fire in his cell, killing him. The Ghost Initiative having been exposed, John takes the fall for his wife and hands in his resignation. Oliver and Rene work together with Emiko to find out who killed her mother. In her hideout, Emiko meets Dante, revealing they are working together.

Team Arrow works with the SCPD to take down an operation that is manufacturing poison bullets. When the initial attempt as part of the SCPD fails, Team Arrow goes rogue and successfully takes down the operation as vigilantes, resulting in Mayor Pollard creating a special vigilante task force that is sanctioned by the SCPD and made up of Team Arrow. Dinah, who can no longer fully perform the Canary Cry following her injury, decides to return to the field as part of the task force. Laurel visits Slabside, where Ben Turner tells her that he witnessed the new Green Arrow kill Diaz. Laurel confronts Emiko, who states that no one would believe Black Siren, a former criminal.

In the flashforwards, Mia and William follow Felicity's coordinates toGalaxy One headquarters. They are almost caught, but are saved by Connor, who reveals himself as an agent ofKnightwatch, a "good version of A.R.G.U.S." Meanwhile, Rene confronts Dinah, Roy, and Zoe, revealing that Galaxy One plans to blow up Star City to rebuild it like the Glades, but the city will be evacuated beforehand. The three discover that a terrorist organization namedEden Corps, that uses Galaxy One as a front, paid the SCPD to fake Felicity's death. Mia, William, and Connor enter the headquarters' sublevels, where they find an imprisoned Felicity who claims that the building houses the bombs to be used on Star City. The others reunite with the group before they meet Rene, who has learned that the bombs are already on-site and that there are no plans to evacuate. The group infiltrates a party where Mia destroys an electronic device held by Galaxy One headKeven Dale, disabling the bombs. Dale unveils a helmet that would enable Galaxy One to take the Archer program global. Felicity makes amends with Mia, stating that her grudge with Galaxy One is personal.

Laurel goes on the run and partners up with a former associate namedShadow Thief. Felicity discovers that Emiko framed Laurel, but Dinah informs her that Laurel has gone back to committing crime as Black Siren. After failing to convince Laurel to come back, Felicity recruitsSara Lance to come to her and Dinah's aid. The three confront Laurel about what she wants to be, which leads to her turning on Shadow Thief. Dinah clears Laurel's reputation by claiming she went undercover. Laurel decides to return to Earth-2 to right her wrongs as Black Canary. Meanwhile, Oliver and Diggle track the rifle used to kill Emiko's mother and discover it belongs toKodiak of the Longbow Hunters. Through interrogation, they find out he was hired by Dante.

With the Ninth Circle after aDepartment of Defense vault drive, Diggle contacts his stepfather,General Roy Stewart, but Stewart refuses to give up classified intel. After they steal Archer from Smoak Tech, Stewart reveals the drive contains an asset list the Ninth Circle can now track. While securing the assets, Diggle and Stewart are captured by Dante. Stewart surrenders codes for a biological weapon called Cygnus X-1 when Dante starts torturing Diggle. The two call in Team Arrow with the Spartan helmet and escape. Team Arrow tracks Archer and the Ninth Circle to Cygnus X-1. While the rest destroy Archer, Oliver confronts Emiko, telling her Dante had her mother killed. Dante exfiltrates Emiko and they escape with Cygnus X-1, after which Emiko kills Dante. Diggle makes amends with Stewart after learning he is blameless in his father's death. Alena copied Archer's root code and suggests a partnership withMagnus Labs to expand it, but Felicity refuses to rebuild it.

Oliver is trapped one floor below his team. The physical and psychological trauma causes him to hallucinateTommy Merlyn talking to him about how to deal with Emiko. Oliver refuses to listen to Tommy about using the best parts of himself to save her until he envisions a scenario where his vendetta against Emiko leads to the deaths of his teammates. Team Arrow locates Oliver and saves him. Meanwhile, the SCPD raids Smoak Tech, accusing Team Arrow of both the cover-up and the biological weapon, which was traced to Archer. Felicity and Alena escape to the bunker, where they are confronted by Emiko, who leaves after Felicity reveals she is pregnant. Emiko is revealed to have stolen Oliver's arrows and attacks the SCPD as the Green Arrow, stealing the weapon back. Oliver tries to reason with Emiko and refuses to take the opportunity to kill her, allowing her to escape.

Emiko spreads the virus throughout the city and holds the detonator in the formerQueen Consolidated building. Team Arrow, with Curtis, Laurel, and Ben Turner, evacuates it and disables the relay to the other bombs, while Oliver confronts Emiko, pleading for her to abandon the dark path.Beatrice informs Emiko that her failure to destroy Star City, while publicly exposing the Ninth Circle, has led to the council turning on her. Oliver and Emiko fight the Ninth Circle together, but Emiko is mortally wounded by Beatrice and tells Oliver to hide Felicity and their baby, before he escapes the exploding building. Oliver and Felicity invent the Mark of Four before leaving Star City for Bloomfield. Following Mia's birth, the Monitor appears, demanding Oliver hold up his part of their deal.^[a] Oliver leaves with him to assist in the oncoming crisis, despite learning he will die in it.