Oliver continues his battle with Cayden James. Dinah and Oliver have a major disagreement that endangers the life of one of their own.

Cayden James ups the ante by launching his plan to take control of every aspect of the city. Despite the scope of Cayden’s plan, Oliver is determined to foil it with just the Original Team Arrow – and without the aid of Rene, Dinah, or Curtis. But things get complicated when William is endangered as a result of Cayden’s handiwork.

Despite losing half his team, Oliver remains confident that he, Felicity and Diggle can stop Cayden James and Black Siren. However, when he discovers one of Cayden’s secrets, he decides to team up with an unlikely ally. Meanwhile, Dinah spends time with Vince.

Quentin Lance is kidnapped by Black Siren and Cayden James, who are looking to trade Lance’s life for a weapon of mass destruction. Oliver and Team Green Arrow must figure out a way to save Lance while still keeping the city safe.

Barry and Iris’s wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth’s mightiest heroes – Green Arrow, Supergirl, The Flash and White Canary – lead their teams into battle to save the world.

The crossover starts on Supergirl S03E08 Crisis on Earth X (I). It continues on The Flash S04E08 Crisis on Earth-X (III) and DC’s Legends of Tomorrow S03E08 Crisis on Earth X (IV).

Oliver celebrates Thanksgiving with his family but the happy moment is interrupted. Meanwhile, Black Siren returns to wreak havoc on the holiday.

As Slade continues to uncover clues about his son’s last few years, Oliver makes a big decision. Meanwhile, the Green Arrow leads the team into battle against “The Dragon,” a villain who is stealing valuable tech in Star City.

Slade returns and asks Oliver for help in tracking down his son. When they learn Joe has been taken hostage by mercenaries, their mission to save him gets complicated by a terrible revelation that could shatter Slade’s hopes of reunion forever. Meanwhile, Vigilante reappears in Star City.

Just as Oliver starts to get things in order, Black Siren launches another attack on the citizens of Star City.

A rogue black ops team led by Onyx breaks into Kord Industries and steals something lethal. Oliver struggles to connect with William so he reaches out to a surprising source for help.

Oliver tries to balance being the mayor, Green Arrow and a father to William. Anatoly returns to Star City with a deadly agenda.

Oliver deals with the fallout of the explosion on the island.

Oliver assembles a group of unlikely allies – Slade, Nyssa, Merlyn and Digger Harkness – to engage in an epic battle against Chase and his army.

Black Siren returns to give Chase help; Felicity plans a birthday party for Oliver; Lance is angry with Rene for missing the custody hearing about his daughter.

Oliver faces the forced release of criminals prosecuted by Adrian Chase, while a crate is delivered to Oliver’s office containing a corpse in concrete.

Oliver and Felicity get trapped in the bunker together, while Diggle and Lyla deal with marital issues.

Oliver, Team Arrow, ARGUS and the SCPD kick off a citywide manhunt for Adrian Chase. Helix tells Felicity they have a way to find Chase but they will need something big, and illegal, from her in return.

Diggle and Felicity are shocked by Oliver’s decision to ask the Bratva for help in taking down Prometheus.

Prometheus goes to extreme lengths to destroy Oliver. In flashbacks, Oliver’s violent tendencies come to a head in a confrontation with Anatoly.

Oliver gets closer to the truth about Prometheus. Meanwhile, Helix refuses to continue helping Felicity until she does a favor for them.

Oliver faces his biggest challenge yet as mayor. Felicity continues down her dark path with Helix. After Vigilante attacks Oliver while he’s acting as the mayor, Diggle leads the team in a mission to stop Vigilante once and for all.

China White, Cupid and Liza Warner break out of Iron Heights and head to Star City for revenge. Oliver tries to bring in the newly formed girl gang but the ACU intervenes mid-fight. To his surprise, they are there to arrest the Green Arrow for the murder of Det. Malone. Meanwhile, Lance feels responsible for the prison break after Warner tells him she heard about him working with Damien Darhk.

A traumatic attack on City Hall triggers painful memories for Rene about his family. Flashbacks reveal how Rene went from simple family man to a hero named Wild Dog. Meanwhile, Oliver must deal with the perpetrator behind the attack and realizes the best way to do so is as Mayor Queen instead of the Green Arrow. Tensions run high in the Arrow bunker.

A mission takes Oliver, Felicity and team to Russia where they meet up with Oliver’s old friend, Anatoly. Meanwhile, fresh out of rehab, Lance returns to the mayor’s office ready to get back to work. However, when Susan asks for an interview with Lance to discuss his addiction, he balks and it’s up to Rene to help keep things on track.

In his quest to take down Kovar, Oliver gets help from a surprising source – Talia al Ghul. However, when she reveals what she wants from him in exchange, Oliver isn’t sure he can accept her help. Felicity attempts to hack the NSA to help free Diggle but when her online efforts are flagged, she faces off against an unknown adversary. Meanwhile, Curtis tells the team about a female vigilante, Tina Boland, he uncovered online who has been wreaking havoc all over the country.

Worried that Prometheus is right and he is truly a killer at heart, Oliver looks for any ray of hope and finds it in what seems to be the miraculous return of Laurel Lance. However Felicity, still reeling from Detective Malone’s murder, is bent on revenge – she wants to stop Prometheus at any cost. While in prison, Diggle fights for his life.

After Prometheus attacks Curtis, Oliver realizes Prometheus knows all of Team Arrow’s secret identities and is planning to come for them one by one. Felicity and Detective Malone discover a clue that links Prometheus to Oliver’s past.

Oliver wakes up to a life where he never got on The Queen’s Gambit. Robert and Moira Queen are alive and well. Laurel is his loving fiancée and their wedding is imminent. Everything seems perfect, but Oliver starts to notice small imperfections that make him question this new reality. Meanwhile, Felicity and the recruits take on a new threat with help from The Flash and Supergirl.

The crossover starts on Supergirl S02E08 Medusa (I) and The Flash S03E08 Invasion! (II). It continues on DC’s Legends of Tomorrow S02E07 Invasion! (IV).

When the bodies of two criminals are dropped at SCPD, Oliver realizes there is a new Vigilante in Star City. The team is split about whether they should stop someone who is helping keep the city safe. Diggle is frustrated with his new situation and Thea fights for Lance who confesses a shocking secret. Meanwhile, in the flashbacks, Oliver finally sits down with Konstantin Kovar.

Prometheus claims two more victims, and Oliver realizes that the killings are related to the people on his father’s list. His recruits aren’t happy to hear that Oliver used to be a serial killer. In the past, Oliver finally meets Kovar and may not live to regret it.

When Tobias Church captures and tortures one of Oliver’s new recruits, Oliver must turn to an old friend, Christopher Chance AKA the Human Target, for help. Meanwhile, Felicity’s worlds collide when Detective Malone joins the ACU.

Oliver and Lyla team up on a secret mission for Diggle. Felicity finds out and disapproves of the plan and opts to stay behind. When Tobias Church launches a deadly assault against the city, Felicity must decide if she wants to send the recruits out sans the Green Arrow.

The Green Arrow is forced to face a powerful new drug dealer when Wild Dog goes off on his own.

Oliver recruits Curtis, Wild Dog and Evelyn Sharp for his team, but his training methods prove to be too much for some to handle. In flashbacks, Oliver continues his initiation into the Bratva.

A deadly new criminal, Tobias Church, threatens Star City, which forces Oliver to consider forming a new team of superheroes to help him do battle. In flashbacks, Oliver faces off against the Bratva in Russia.

Oliver teams up with a surprising force in an attempt to stop Damien Darhk and his magic once and for all.

Following the shocking events in the previous episode, Oliver and Diggle race to rescue Thea, while Felicity, Curtis and Noah join together to stop Darhk.

When Team Arrow learns what Damien Darhk’s next move is Felicity realizes she needs to ask her father, Noah Kuttler, for help. Noah and Oliver have a heart to heart talk that leaves Oliver rattled.

As Oliver and Felicity look for a magical solution to defeat Darhk, a vengeance-driven Diggle gets a lead on Andy’s whereabouts and heads off to confront his brother. Meanwhile, Alex takes Thea on a vacation that quickly turns into a nightmare.

Oliver and the team struggle to come to terms with Laurel’s death, especially Diggle who is overwhelmed with guilt for choosing to believe Andy had changed. Meanwhile, Lance refuses to believe his daughter is really gone and asks Nyssa to help bring her back. A recent Black Canary sighting in Star City only seems to prove his theory that Laurel isn’t actually dead.