When a new threat emerges in National City, Kara/Supergirl teams up with her cousin, Clark Kent/Superman, to stop it. Kara is thrilled to have family in town but it leaves Alex feeling a bit left out. Meanwhile, J'onn and Supergirl are stunned by the pod that came crashing to Earth.

Cadmus attacks National City with a kryptonite powered villain who ends up seriously hurting Supergirl. Superman blames J'onn because the Kryptonite was stolen from the D.E.O.. Meanwhile, Kara's first day at her new job doesn't go as planned after she meets her new boss, Snapper Carr.

An attack is made on the President as hot-button, alien vs. human rights issues heat up in National City. Supergirl and the D.E.O. are assigned to protect the President and bring in the responsible party. Alex teams up with Detective Maggie Sawyer to investigate the case while Kara searches for a recently escaped Mon-El, who she fears may be the alien behind the assault.

When Kara and Alex investigate the murder of an unregistered alien, the trail leads to an alien fight club run by Roulette, the ringmaster who commands aliens to fight in mortal combat for the entertainment of rich humans. While trying to stop the fighting, Supergirl and Martian Manhunter find themselves up against a surprising opponent. Meanwhile, Hank is thrilled to have found another Martian and tries to get to know M'gann better. Supergirl takes Mon-El under her wing and begins to train him.

Supergirl must beat a ruthless new gang who has been armed with dangerous new alien technology. When Cadmus sends a video to the D.E.O., the team realizes Cadmus is the one staffing the criminals for a secret mission. Meanwhile, Kara gets Mon-El a job as an intern at CatCo, James makes an important decision and Lena invites Kara to attend one of her fundraisers.

Guardian debuts to lend a hand after a parasite alien drains Supergirl of her power. Mon-El considers a less than desirable new career which then leads him to contemplate his motives. Alex struggles with a new reality.

Barry is living his dream life – his parents are alive, he's asked Iris West on a date and he can finally be a normal guy as Central City has another speedster, Kid Flash, running around saving the city. When Barry starts forgetting parts of his old life, the Reverse Flash taunts his nemesis and tells him that there will be serious repercussions for Barry and the ones he loves if he continues to live in this alternate universe.

Barry realizes the effects from Flashpoint are much greater than he thought. Meanwhile, Barry meets new co-worker Julian Albert and is surprised by Julian's immediate disdain for him.

Barry and Team Flash are thrilled to reunite with Earth-2 Wells and Jesse. Wells confides to Barry and Caitlin that Jesse has all the powers of a speedster and has been saving people on his Earth. He is concerned about her safety and wants them to talk her out of using her powers. Meanwhile, Magenta, a new meta who can control metal, terrorizes the city.

Barry continues to train Jesse and when a new meta human, Mirror Master, appears on the scene he lets her tag along. Mirror Master has teamed up with his old partner, Top, and is looking for Snart to even a score. Jesse is quick to join the chase but defies one of Barry's orders which results in disastrous consequences.

Desperate to understand what is happening to her, Caitlin visits her mother, Dr. Tannhauser, a renowned biomedical researcher, in the hopes that her mother can provide some answers about Caitlin's growing meta-human powers. However, when Dr. Tannhauser treats her daughter like a test subject, Caitlin grows cold and brings up past wounds causing the two to have a major blowout. Meanwhile, after a mysterious new meta-human attacks Central City, Barry tries to convince Julian to let him assist on the case.

When Wally starts having dreams about being Kid Flash, Barry realizes he has to tell Wally, Iris and Joe about what happened to Wally in Flashpoint in order to keep him safe.

Caitlin uses her powers to save Barry but as her mother predicted, the effort unleashes her inner Killer Frost. Killer Frost goes on a rampage looking for Dr. Alchemy, kidnapping Julian and battling both The Flash and Vibe. Meanwhile, Joe and H.R. have a heart to heart talk.

While Guardian tries to clear his name after being accused of a murder committed by another vigilante, Supergirl heads out on a solo mission to rescue Mon-El who has been captured by Cadmus. While fighting to free Mon-El, Supergirl comes face to face with Cyborg Superman.

After Laurel's death and the departures of both Diggle and Thea from Team Arrow, Oliver takes to the streets solo to protect Star City. With Felicity guiding him from the bunker, Oliver is forced to deal with a city that has become overrun with both criminals and a slew of new (and inexperienced) vigilantes. When a deadly new criminal, Tobias Church, enters the picture, Oliver realizes the best thing for the city might be a new team of superheroes. Meanwhile, the flashbacks take us to Russia where Oliver faces off against the Bratva.

Oliver's new recruits for Team Arrow are Curtis, Wild Dog and Evelyn Sharp. Unfortunately, the Green Arrow's training methods prove to be too much for some of them to handle. Meanwhile, in the flashbacks, Oliver's initiation into the Bratva continues.

After the defeat of the immortal villain Vandal Savage and the exposure of the corrupt Time Masters, a new threat emerges. Dr. Nate Heywood, an unconventional and charming historian, is thrust into the action. After making a shocking discovery, Nate seeks out Oliver Queen for help in finding the scattered Legends. Once reunited, the Legends continue their new mission to protect the timeline from temporal aberrations – unusual changes to history that spawn potentially catastrophic consequences.

The Legends travel to Nazi-occupied Paris, but find themselves surrounded by the Justice Society of America (AKA JSA.) The Legends force their way into the JSA's mission to intercept and seize a mysterious package. Nate is desperate to prove that he should be part of the team, but he has a secret that he shares with his grandfather Commander Steel that might make it difficult. Meanwhile, Stein has stepped in as the leader with Rip gone, but when decisions aren't being made Sara seems to be the one calling the shots.

Nate is shocked to learn that he has powers but then accidentally lands himself and Ray in Feudal Japan. After Sara convinces their stowaway Amaya, AKA Vixen, that Rory is not a murderer, they all agree to find Nate and help him master his powers in order to defend the Japanese village from the Shogun and his army of samurai warriors. Meanwhile, Jax and Stein stay back to help fix the ship and find a secret compartment but decide not to tell the rest of the team what they learn.

Now that Oliver has his new team, they are ready to hit the streets but Oliver doesn't feel they are ready. Headstrong Wild Dog defies the Green Arrow's orders and sets out on his own after a new drug dealer, Derek Sampson, who is terrorizing Star City. Sampson proves more powerful than Wild Dog and it is up to the Green Arrow to go head to head with Sampson to save his teammate.

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.

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.

When Prometheus ups his killing spree, Oliver searches for connections between the victims. Felicity and Curtis discover the victims have a mysterious link to Oliver's past and this new secret could upend his new team. Meanwhile, Thea has a heart-to-heart with Lance, and Felicity considers telling Malone the truth about her work.

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.

When the Legends discover a time aberration in 1863, they find themselves fighting for survival during the Civil War with Confederate soldiers who have been turned into zombies. With the Civil War outcome hanging in the balance, Jax must participate in a daring mission by going to a slave plantation with Amaya. Meanwhile, Sara begins to feel the burden of the decisions she has to make as the leader, and Ray struggles to find his purpose on the team.

When the Legends trace a timequake to President Reagan's White House, they are shocked to discover their old enemy Damien Darhk is now a Senior Adviser to Reagan. As the team works to uncover what Darhk has up his devious sleeve, Sara struggles with the choice of getting revenge or helping with the team's larger mission. Thinking that the JSA members could be of help, Amaya and Nate break into the JSA and are surprised at what they find. Meanwhile, Stein tries to prevent his younger self from creating an even bigger time Aberration.

The Legends are still reeling from the news that their time travel-nemesis is a speedster when they are alerted to an Aberration in the Old West. When the Legends arrive they find their old friend Jonah Hex in trouble with his arch-nemesis, Quentin Turnbull. The team soon discovers that they need to stop Turnbull and his gang from conquering the West and branding it his own lawless territory. To Hex's surprise, Sara is in charge and dispatches the team. Meanwhile, Nate, Ray and Jax try to infiltrate Turnball's gang, but find themselves in a shootout.

Eliza comes to town to celebrate Thanksgiving with her daughters. Alex decides it's time to come out to her mother; Kara is shocked when Eliza suggests Mon-El has feelings for her, and Winn and James consider telling Kara the truth about the Guardian. Meanwhile, Cadmus unleashes a virus that instantly kills any alien in the vicinity so Kara enlists an unexpected ally - Lena Luthor. The epic superhero crossover kicks off tonight when Barry Allen and Cisco Ramon seek Kara's help with an alien invasion on their Earth.

When aliens called the Dominators attack Central City, Barry speeds over to Star City to ask the Green Arrow for help in stopping them. Realizing the battle against the Dominators is bigger than they thought, they track down the Legends of Tomorrow, and Barry and Cisco create a breach to bring back a secret weapon – Supergirl. 

Oliver wakes up to a life where he never got on The Queen's Gambit. Robert and Moira 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.

This is the 100th episode.

After learning the Dominators' plan for the world, the Legends must work together with The Flash, Supergirl and Green Arrow to kill them once and for all. Meanwhile, Stein figures out, with the help of others, how the team can terminate the Dominators, but is distracted by the aberration he realizes he created in 1987.

With Alchemy and Savitar still looming threats, Barry is unable to focus on the Christmas holiday, and especially his relationship with Iris. Determined to stop Savitar, Barry goes to Earth-3 to get advice from Jay Garrick. Wally wants to help Barry fight Savitar and reveals that he's been training with H.R., which doesn't go over well with Barry. As Cisco faces his first Christmas without his brother Dante, old wounds are reopened.

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.

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.

When a new Time Aberration is discovered by the Legends, they find themselves headed to 1927 Chicago. The Legends quickly realize that they have been set up by Eobard Thawne, Damien Darhk and the newest member of the Legion of Doom, Malcolm Merlyn. While everyone is trying to help fix what they think is the mission, Jax encourages a reluctant Stein to share his secret with the other Legends. Meanwhile, Rory gets an unexpected visitor and is not sure how to handle it.

When Damien Darhk and Malcolm Merlyn try to capture Rip Hunter in 1967, they create an Aberration big enough to draw the attention of the Legends. However, when the team arrives they discover that Rip has no memories of his past due to “time drift” and is just a graduate film student. After trying to convince Rip of who he was, they discover that he possesses an incredibly powerful artifact known as the Spear of Destiny, which the Legion of Doom is after. 

The Legends are determined to find and rescue Rip, but first must focus on locating the Spear of Destiny. Stein thinks he has the perfect person to help but knows involving her will be risky. Meanwhile, Malcolm Merlyn and Damien Darhk realize that Thawne is pitting them against each other.

When The Legends find a new Time Aberration they learn they must travel to the winter of 1776 to protect George Washington and the American Revolutionary War. Unfortunately, things don't go as planned, forcing Sara to send out Nate and Amaya to help. Meanwhile, Jax and Stein who are busy protecting the incapacitated Waverider from their new enemy, are forced to step into roles that they don't think they are prepared for.

Kara is moved by the story of a missing woman named Izzy and decides to investigate. Kara takes Mon-El  find themselves thrust through a portal to another planet, Slaver's Moon, where the downtrodden are sold as slaves. Slaver's Moon has a red sun, which means Kara and Mon-El are stripped of their powers and stuck on the planet with no way home. Meanwhile, back on Earth, Alex blames herself for Kara's disappearance, fearing she's become too focused on her new relationship with Maggie and too complacent in watching out for her sister.

After Livewire seemingly breaks out of prison, Supergirl is intent on recapturing her. After training Mon-El, Supergirl takes him with her when she sees Livewire attack the NCPD but things go awry when Mon-El puts Supergirl before the citizens of National City. Meanwhile, James decides to come clean with Kara and M’gann, has a psychic attack and collapses into a coma.

Barry is tormented by his vision of the future where Iris is murdered by Savitar. When a criminal named Plunder shows up in Central City, Barry recalls the villain's presence in his vision of the future and fears that if he catches Plunder, it will cement Iris’ fate. Confused about Barry's hesitation to stop Plunder, Wally decides to step in as Kid Flash. Caitlin offers Julian a job.

H.R.'s past catches up with him when a bounty hunter with vibe powers named Gypsy arrives in Central City to bring him back to Earth-19 to stand trial for his crime. It turns out inter-dimensional travel is illegal on their Earth. H.R. surrenders but when Barry and Cisco find out that H.R.’s only hope would be to challenge Gypsy to a fight to the death, they intercede and Cisco offers to fight Gypsy instead.

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.

Barry and the team at S.T.A.R. Labs work together to bring down Clive Yorkin, a criminal meta-human who is methodically killing people by causing them to decompose at an accelerated rate. Joe becomes his next target but it's Iris who is caught in the crossfire. The Flash mentors Kid Flash and begins to elevate the newer speedster's training to another level.

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.

Armek, a White Martian, descends on National City intent on taking M'gann back to Mars to face her punishment as a traitor. J'onn and Supergirl determine the best way to keep M'gann safe is to bring her to the D.E.O.. However, when it is revealed that Armek shape-shifted into M'gann and is now loose in the building, the team realize he could be disguised as any one of them.

After Metallo breaks out of prison and frees Lillian Luthor, the police blame Lena for his escape and arrest her. Despite overwhelming evidence, Kara refuses to believe her friend is guilty and fights to clear Lena's name. Flashbacks reveal how Lena came to be a Luthor. Meanwhile, Alex introduces Maggie to the gang.

When Mr. Mxyzptlk, a magical imp, shows up on Earth and declares his love for Kara, she tries to let him down easy, thinking him harmless. However, he decides it's a challenge and starts to wreak havoc on National City. Mon-El has seen beings like Mr. Mxyzptlk on Daxam and knows how dangerous they can be. He and Kara argue over how to get rid of Mr. Mxyzptlk, further straining their relationship. Meanwhile, Alex and Maggie celebrate their first Valentine's Day together. 

When Jeremiah Danvers is rescued from Cadmus, Alex and Kara are thrilled to have their father back. The Danvers arrange a family dinner to celebrate but things go awry when a suspicious Mon-El starts to question Jeremiah about his sudden return.

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.

When Jesse Quick informs the team that her father has been abducted, Barry, Caitlin, Cisco and Julian voyage to Earth-2 on a rescue mission to save Harry from Gorilla City. As they trek through the forest, Barry and the team are immediately captured and brought to Grodd. Grodd tells them he needs their help to stop Solovar, the leader of Gorilla City, as Solovar wants to invade Earth-1.

When Grodd and his army of gorillas bring the battle to Earth-1, The Flash and team must find a way to stop them before they destroy Central City. Gypsy returns to join the fight. Meanwhile, Jesse Quick decides she wants to stay with Wally on Earth-1.

The Legends continue their quest to hunt down the Spear of Destiny before the pieces fall into the hands of the Legion of Doom. The Legends discover that pieces of the Spear are each being guarded in different time periods by members of the JSA. Their first stop is the future where they find Dr. Mid-Nite which eventually leads them to the past and King Arthur's Camelot, where Stargirl is protecting her piece of the Spear. In order to protect the Spear shard from the now-evil Rip Hunter, the Legends must join forces with the Knights of the Round Table.

After capturing Rip, he forces the Waverider to crash, leaving the Legends stuck seventy million years in the past. Ray leads Amaya and Nate to recover a vital piece of the ship. In an effort to get the “good” Rip back, Rory suggests they enter Rip's mind, but what Sara and Jax discover in his subconscious is not pleasant and they must fight evil versions of themselves. Meanwhile, Nate and Amaya continue to get closer, but it could cause serious ramifications.

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 Detective Malone. Meanwhile, Lance feels responsible for the prison break after Warner tells him she heard about him working with Damien Darhk.

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.

As Alex searches for Jeremiah and Kara investigates a series of alien kidnappings, the sisters realize they must break the rules to foil a new Cadmus plot. In an effort to get Snapper Carr to run a story that would help her stop Cadmus, Kara agrees to set up an interview between Snapper and Supergirl.

While training with Barry, Wally starts to have visions of Savitar, which he hides from the team. A dangerous secret threatens Barry and Iris' happiness.

Desperate to stop Savitar and save his friends, Barry turns to the speed force for answers. H.R. gives Jesse some advice.

When the Legends track Commander Steel to NASA Headquarters in 1970, they learn where Nate’s grandfather hid the last fragment of the Spear of Destiny. The team notices a time aberration during the Apollo 13 mission and believes that the Legion of Doom might be involved. As the Legends journey into space to intercept Apollo 13, the Waverider suffers massive internal damage and Ray’s life is left in jeopardy when he is stranded on the moon. Meanwhile, tension grows between Rip and Sara as to who is the leader of the team.

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

A new villain comes to National City, putting Supergirl on high alert. Meanwhile, Winn's girlfriend, Lyra, gets Winn in trouble with the law. Maggie attempts to help Winn but old loyalties get in the way. The Music Meister attacks Supergirl.

Barry and team are surprised when Mon-El and Hank Henshaw arrive on their Earth carrying a comatose Supergirl who was whammied by the Music Meister. Unable to wake her up, they turn to Team Flash to save her. However, the Music Meister surprises The Flash and puts him in a similar coma, one that Team Flash can't cure. Kara and Barry wake up without their powers in an alternate reality where life is like a musical and the only way to escape is by following the script, complete with singing and dancing, to the end.

The Legends must devise a plan to retrieve the last remaining fragments of the Spear of Destiny from the Legion of Doom. They find themselves in France at the height of World War I faced with the knowledge that they must destroy the mystical object. They enlist the help of a soldier by the name of John Ronald Reuel Tolkien and find that the Spear is leading them into the heart of the war. Meanwhile, the team must all resist the temptation of the Spear, and the return of a former teammate.

Prometheus goes to great lengths to break Oliver. Meanwhile, in the flashbacks, Anatoly becomes worried about Oliver's increasingly violent tendencies, which come to a head in a brutal confrontation.

Diggle and Felicity are shocked by Oliver's decision to call on the Bratva to help take down Prometheus. Concerned the Bratva may overstep, Diggle has a hard conversation with Oliver about what happens if things go south. Meanwhile, Felicity learns something shocking at Helix.

A large bounty is put out on Supergirl and aliens from far and near attack National City intent on taking out the woman of steel. Alex and Maggie run into Maggie's ex-girlfriend, Emily, who is in town for a week. J'onn gets an interesting order from President Marsdin.

The Flash battles Abra Kadabra, a villain from Earth-19, who makes him a tempting offer – release him and Abra Kadara will reveal Savitar’s true identity. Desperate to save Iris, Barry considers taking the deal but Gypsy breaches in to capture the villain for her own reasons and during the melee, Abra Kadabra manages to escape. Barry is furious that Gypsy interfered but Gypsy refuses to back down, forcing Cisco to take sides. Meanwhile, Julian is still a bit cold towards Caitlin but when she is severely injured in a battle with Gypsy, he rushes to her side.

Barry travels to the future to find out Savitar's still unknown identity in the hopes of saving Iris. Upon his arrival in 2024, Barry encounters future versions of his Team Flash friends, who, following the death of Iris, have become very different people, profoundly impacted by their showdown with Savitar. It will be up to Barry to infuse a sense of hope back into the team, as he proves to be the hero his future friends have been waiting for. Meanwhile, back in 2017, the hunt for Killer Frost continues.

Barry and the team meet Tracy Brand, a scientist, who may be the key to stopping Savitar. Unfortunately, Killer Frost is also after Tracy so Team Flash must battle their old friend, which proves to be particularly difficult for Cisco. Joe and Cecile’s relationship takes a big turn.

Barry takes drastic measures to stop Savitar. Meanwhile, H.R. continues to push Tracy Brand to design the trap for Savitar and Killer Frost returns with an interesting proposal. 

With only 24 hours left until Savitar murders Iris West, Barry struggles to save the woman he loves and makes the choice to use any means necessary to do so. Realizing he has one option left to save her, The Flash turns to Captain Cold for help.

With nothing left to lose, Barry takes on Savitar in an epic conclusion to season three.

Oliver, Team Arrow, A.R.G.U.S 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.

Lena’s ex-boyfriend, Jack Spheer, comes to National City to unveil his big breakthrough in nano-technology, which has the potential to eradicate all diseases. Lena asks Kara to attend Jack’s conference with her for support. When Kara sees Snapper in attendance she’s inspired to tap back into her reporter skills and questions Jack on his discovery, which ultimately leads to a bigger investigation that puts everyone in danger.

After obtaining the Spear of Destiny, the Legion of Doom rewrites reality, leaving the Legends changed, perhaps forever. Frightfully, the Legends' and the world's hopes rest with Rory, but being the "hero" is not easy for him. Meanwhile, there is tension within the Legion of Doom and the reason why the Spear of Destiny needs to be destroyed is revealed.

As the Legends are about to take off for their next destination, a massive timequake rocks the ship. In order to try and fix what has happened, they are forced to break the one cardinal rule of time travel. But if they are able to destroy the spear, they will face the ultimate consequence.

Alex is kidnapped and the kidnapper threatens to kill her unless Supergirl releases a notorious criminal from prison. Supergirl and Maggie have always had different approaches to apprehending criminals but this time they must work together to save Alex. Meanwhile, Rhea has an interesting proposal for Lena.

When an alien attacks National City, Supergirl and the DEO learn the alien is a Phorian, an otherwise peaceful race with telekinetic powers. Guardian gets a lead on the Phorian's address but instead of finding the culprit, he finds a very scared boy named Marcus. Marcus will only trust James so it is up to Guardian to stop the attacks on the city. Rhea's plan escalates.

Supergirl grapples with whether or not to obey the President’s orders regarding Rhea’s latest actions. Meanwhile, Cat Grant returns to National City.

Supergirl challenges Rhea to battle to save National City. Meanwhile, Superman returns and Cat Grant offers Supergirl some sage advice.

Things get intense when Oliver and Felcity are trapped in the bunker together. Meanwhile, Lyla and Diggle deal with their marital issues.

Oliver returns to the mayor's office and faces one of his most pressing issues yet – the forced release of dozens of violent criminals prosecuted by Adrian Chase. Meanwhile, a crate is delivered to Oliver's office containing a mysterious corpse encased in concrete.

Black Siren returns to help Chase. Felicity organizes a birthday party for Oliver while Lance is furious after Rene misses the custody hearing for his daughter.

The battle between Oliver and Adrian Chase culminates in a final epic battle on Lian Yu. After recent events, Oliver decides to recruit a group of unlikely allies - Slade, Nyssa, Merlyn and Digger Harkness - to defeat Chase. However, Chase has his own army - Black Siren, Evelyn Sharp and Talia al Ghul - and the forces collide in an explosive season finale.