Episode 1 : City of Heroes
In the season premiere, Oliver must transform from vigilante to hero. Diggle and Felicity travel to the island of Lian Yu in search of Oliver, who left Starling City after the devastation of The Undertaking and his failure to avert it. Convinced to return home, Oliver finds that things are in much worse shape than he imagined ? Isabel Rochev (recurring guest star Summer Glau) is preparing a hostile takeover of Queen Consolidated, Thea refuses to visit Moira in jail, Roy is trying to fill the void left by the Arrow's absence, and Laurel is working with the District Attorney's office to take down the vigilante. Meanwhile, flashbacks to the island show Oliver's mentors Slade (new series star Manu Bennett), Shado (guest star Celina Jade) and Oliver in a desperate situation.
Episode 2 : Identity
DC Comics' Bronze Tiger and China White wreak havoc on the Glades. Oliver finds out that medicine being sent to Glades Memorial Hospital is being hijacked by thieves ? and without an influx of supplies, the hospital will close. When Roy attempts to stop the thieves, he fails and is arrested by Officer Lance. Oliver gets into a heated battle with China White (recurring guest star Kelly Hu) and her new partner, Ben Turner, aka the Bronze Tiger (guest star Michael Jai White), over the supplies. Meanwhile, Laurel makes plans to catch the Arrow, and Thea gives Roy an ultimatum.
Episode 3 : Broken Dolls
Officer Lance's past puts Laurel in danger. Lance learns a criminal named Barton Mathis (guest star Michael Eklund), whom he put away years ago, broke out of prison during the quake and is back to torturing and murdering women. Felicity offers herself as bait so Arrow, Diggle and Lance can catch this villain, but the plan goes awry. Furious, Mathis kidnaps Laurel in retaliation and plans to murder her while Lance watches. Meanwhile, Thea and Oliver are stunned when District Attorney Adam Donner (guest star Dylan Bruce) seeks the death penalty for Moira. Oliver asks Roy to help him find the Canary (guest star Caity Lotz).
Episode 4 : Crucible
Oliver meets the Canary. Oliver discovers a man who goes by the name "The Mayor" (guest star Cle Bennett) is bringing illegal guns in to The Glades, so Oliver sponsors a "Cash for Guns" event to help clean up the city. Unfortunately, The Mayor crashes the event with his gang and seriously injures Sin (guest star Bex Taylor-Klaus). The Canary is furious when she learns her friend is in the hospital and sets out for revenge. Meanwhile, Felicity stuns Oliver with a bit of information about the Canary's identity, Donner asks Laurel to dinner, and Diggle reconnects with an old friend.
Episode 5 : League of Assassins
The Canary sings! While Oliver tends to the Canary's wounds, he tries to get her to talk about where she came from, but she refuses. But when Oliver and the Canary are attacked at the Queen mansion by a trained killer from the League of Assassins, she confesses to how she's connected with the nefarious group. Meanwhile, with Moira facing multiple counts of murder and conspiracy for her part in the destruction of The Glades, the Assistant District Attorney offers her a choice ? plead guilty now and avoid the death penalty or take your chances in court. Thea begs her mother to fight for her life but Moira seems resolute about taking the offer. Meanwhile, Oliver is furious with Laurel for joining the prosecution's team on his mother's case.
Episode 6 : Keep Your Enemies Closer
Amanda Waller (guest star CYNTHIA ADDAI-ROBINSON) sends A.R.G.U.S. agents to kidnap Diggle. Waller informs Diggle that Lyla (guest star AUDREY MARIE ANDERSON) has gone missing after following a lead on Deadshot (recurring guest star MICHAEL ROWE) in Moscow. When Diggle tells the team he's headed to Russia to rescue Lyla, Oliver and Felicity decide to join, but things get messy when Isabel shows up on the tarmac and insists on joining Oliver's "work trip." Meanwhile, Moira's lawyer, Jean (guest star TERYL ROTHERY), tells Thea that dating Roy, a known criminal, is hurting her mother's case.
Episode 7 : State v. Queen
Oliver is concerned when a mysterious illness sweeps the city, infecting hundreds of people ? including Diggle. Oliver discovers Vertigo in Diggle's blood and realizes Count Vertigo (recurring guest star SETH GABEL) has broken out of prison and is once again distributing his drug. Meanwhile, Moira goes on trial for her participation in the Undertaking. When ADA Adam Donner collapses in court with Vertigo symptoms, Laurel must step in and try the case against Moira ? leaving Oliver torn between standing by his family during the trial or catching Count Vertigo. The stakes change, however, when Felicity follows a lead and walks straight into a trap set by Count Vertigo.
Episode 8 : The Scientist
After a seemingly impossible robbery at Queen Consolidated, Central City?s police scientist Barry Allen (Grant Gustin) offers to help Oliver and his team.
Episode 9 : Three Ghosts
Oliver is visited by ghosts from the past. After a fight with Cyrus Gold AKA the Acolyte (guest star Graham Shiels), Oliver is drugged and left for dead. Determined to cure him, Felicity makes a risky decision. The cure causes Oliver to hallucinate, and what he sees forces him to confront his past. Meanwhile, Barry continues to help Felicity, and their connection grows stronger. The Arrow asks Lance to look into Gold, but when the stakeout on Gold goes bad, someone is killed. Roy is captured and tortured by Brother Blood (guest star Kevin Alejandro).
Episode 10 : Blast Radius
Oliver must tackle a new threat when bombs start to go off in Starling City. Felicity discovers the person setting them off is Mark Sheffer (guest star Sean Maher), a man who goes by the nickname "Shrapnel." Arrow discovers Shrapnel's next target is Sebastian Blood's "Unity Rally" and tries to talk the alderman out of hosting it, but he refuses. Arrow sets off to stop the bombing, but Shrapnel tricks him and traps him in a bomb-laced antique store where he is unable to move without setting off the device.
Episode 11 : Blind Spot
Arrow teams up with Laurel to find the man in the mask. Conflicted after Laurel reaches out to the Arrow asking him to investigate Sebastian Blood, Oliver is unsure whether to believe her accusations against the man he has publicly supported for mayor, but decides to trust Laurel. However, when the pair gets too close to the truth, Sebastian exposes Laurel's drug addiction and has her arrested. Meanwhile, Roy reveals his new super-strength to Sin who wants to test out his abilities. Unfortunately, Roy isn't able to contain his rage once unleashed and almost kills a man. Back on the island, Oliver is surprised when Sara reveals a secret about Laurel.
Episode 12 : Tremors
Arrow offers to train Roy so he can learn to control his newfound super-strength. However, Roy is a rebellious student and refuses to listen unless Arrow reveals his true identity, which Oliver refuses to do. Meanwhile, the Bronze Tiger (MICHAEL JAI WHITE) escapes from prison and steals Malcolm's earthquake machine to sell to the highest bidder. Oliver, Diggle and Felicity attempt to stop the transfer, but Roy gets in the way, putting everyone in danger. Laurel is disbarred and spirals out of control. Moira is thrilled when Walter (COLIN SALMON) asks her to dinner, but his reason surprises her. Thea encourages her mother to ask Walter to reconcile.
Episode 13 : Heir to the Demon
As Laurel continues to unravel, Oliver and Detective Lance try to convince Sara to stay in Starling City and finally reunite with Laurel and their mother, Dinah (guest star Alex Kingston). However, Sara's fellow League of Assassins member, Nyssa (guest star Katrina Law), comes to bring Sara back to the fold, but when Sara refuses, Nyssa kidnaps Dinah. Realizing she's putting her family in danger by staying in town, Sara considers re-joining the league.
Episode 14 : Time of Death
Oliver brings Sara into the Arrow team. Watching Oliver and Diggle spar with Sara and talk old scars, Felicity starts to feel left out. The team is investigating a villain named William Tockman, a.k.a. The Clock King (guest star ROBERT KNEPPER), who is a brilliant thief armed with technology that can open any bank vault in Starling City. After The Clock King infiltrates the computer systems in the lair, Felicity feels pressure to prove her worth. When she gets a lead on Tockman's whereabouts, she heads out without the team, putting her in peril. Meanwhile, Oliver throws Sara a welcome home party, but Laurel refuses to attend. After Lance makes his case for a family dinner, Laurel acquiesces, but when Oliver shows up with Sara, she loses her temper on both of them.
Episode 15 : The Promise
Oliver is shocked when he learns that Slade has come to Starling City. Back on the island, as Oliver, Slade and Sara prepare to take over the freighter from Ivo (guest star Dylan Neal), Sara pulls Oliver aside and tells him he needs to kill Ivo to prevent him from telling Slade what happened with Shado. Oliver feels immense guilt over the situation but realizes Slade's growing rage from the Mirakuru makes him unpredictable and he could turn on his friends if he thinks Oliver is to blame. Oliver agrees to kill Ivo and the battle begins.
Episode 16 : Suicide Squad
Following Slade's return and his promise to make good on his threat to destroy Oliver's loved ones, Oliver focuses all his energy on preparing for battle with his former friend. Sara tries to help but, fearing for her safety, Oliver pushes her away. Meanwhile, Diggle is recruited by Amanda Waller and A.R.G.U.S. to stop a warlord (guest star Lee Majdoub) he knew from his time in Afghanistan. Always the solider, Diggle agrees to help. However, he's not prepared when Amanda introduces him to the rest of the team ? Deadshot, Bronze Tiger and Shrapnel, all criminals he and Arrow helped put away. Lyla defends the team and explains the world is a complicated place, but Diggle isn't sure he agrees. When the mission takes a dangerous turn, Diggle is forced to make a difficult decision.
Episode 17 : Birds of Prey
When Frank Bertinelli (guest star JEFFREY NORDLING) is arrested, Oliver knows it's only a matter of time before his daughter, Helena, aka The Huntress (guest star JESSICA DE GOUW), returns to town. To make matters worse, Laurel is picked to try Frank's case, putting her right in the path of Helena. Oliver tells Sara he will handle his ex-girlfriend, but when Helena takes hostages at the courthouse, including Laurel, the Canary will stop at nothing to save her sister. When The Huntress and Canary meet, an epic battle begins. Meanwhile, Roy realizes he needs to keep Thea safe, but doesn't like the way he is forced to go about it.
Episode 18 : Deathstroke
Oliver's world starts to crumble when Slade makes his move against Oliver ? and the repercussions are enormous. While Oliver scrambles to protect his family, a key player in his team starts to question Oliver's decisions. Meanwhile, Isabel makes her move to take Queen Consolidated away from Oliver.
Episode 19 : The Man Under the Hood
Deathstroke hits Oliver at home. Oliver, Canary, Diggle and Felicity return to the lair and find Slade waiting for them. An epic battle breaks out and one member of Team Arrow is sent to the hospital. Thea hits her breaking point, but just as Oliver is about to reach her, Slade intervenes and Oliver is faced with a choice ? his battle with Slade or his family. Meanwhile, Laurel struggles with a new secret.
Episode 20 : Seeing Red
The Mirakuru sends Roy into an uncontrollable rage and he unleashes his fury on the city. After Roy's deadly fight with a police officer, Oliver realizes the Mirakuru has taken over Roy completely and must figure out a way to stop him. Things get more complicated after Sara declares that Roy is too far gone and the only way to stop him is to kill him. Meanwhile, Thea believes she can breakthrough to Roy so she goes on camera at Moira's campaign rally to lure him to Verdant. Her ploy works but after Roy attacks Thea, Team Arrow unleashes on him.
Episode 21 : City of Blood
After Slade threatens to take away everything Oliver loves, Oliver decides the fastest way to stop further bloodshed is to surrender to his enemy. Knowing that surrender will surely lead to Oliver's death, Diggle and Felicity go to extreme measures to keep Oliver from confronting Slade. Meanwhile, Thea considers leaving town, and Laurel resumes her crusade against Sebastian Blood. Finally, Slade unleashes his assault on Starling City.
Episode 22 : Streets of Fire
Malcolm Merlyn returns. Oliver rallies his team as Slade's soldiers attack the city. Felicity gets a call from S.T.A.R. Labs with game-changing news and Thea comes face-to-face with her father ? Malcolm Merlyn (recurring guest star John Barrowman).
Episode 23 : Unthinkable
In the Season Two Finale, Oliver must decide once and for all whether he's a killer or a hero when Slade moves forward with his plan to kill one more person in Oliver's life. While Oliver has fought all year to be more than the killer he once was, he's pushed to the edge when Slade kidnaps someone close to Oliver's heart and realizes sometimes it takes doing the unthinkable to stop the monster. Meanwhile, Diggle takes on Amanda Waller with a little help from some friends, and Thea turns to Roy in her time of need.