Diggle and Felicity travel to Lian Yu in search of Oliver, who left Starling City after The Undertaking. Oliver finds that things are in worse shape than he thought – Isabel Rochev 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 Hood's absence, and Laurel is working with the District Attorney's office to take down the vigilante. Meanwhile, flashbacks to the island show Slade, Shado and Oliver in a desperate situation.

Oliver finds out that the medicine sent to Glades Memorial is being hijacked by thieves. Without an influx of supplies, the hospital will close. Roy attempts to stop the thieves, but he fails and is arrested by Officer Lance. Oliver gets into a heated battle with China White and her new partner, Ben Turner, AKA the Bronze Tiger, over the supplies. Meanwhile, Laurel makes plans to catch The Hood, and Thea gives Roy an ultimatum.

Quentin Lance learns a criminal named Barton Mathis broke out of prison during the quake and is back to torturing and murdering women. Felicity offers herself as bait so The Arrow, Diggle and Quentin can catch this villain, but the plan goes awry. Mathis kidnaps Laurel in retaliation and plans to murder her while Quentin watches. Meanwhile, Thea and Oliver are stunned when District Attorney Adam Donner seeks the death penalty for Moira. The Arrow asks Roy to help him find The Canary.

Oliver discovers a man who goes by the name "The Mayor" is bringing illegal guns into 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. 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, Donner asks Laurel to dinner, and Diggle reconnects with an old friend.

Oliver tries to get Sara to talk about where she came from but she refuses. However, after being attacked at the Queen mansion by a trained killer from the League of Assassins, she confesses to how she's connected with to them. Moira faces multiple counts of murder and conspiracy for her part in the destruction of The Glades. Meanwhile, Oliver is furious with Laurel for joining the prosecution's team on his mother's case.

Amanda Waller sends A.R.G.U.S. agents to kidnap Diggle. Waller informs Diggle that Lyla has gone missing after following a lead on Deadshot 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 participating in Oliver's "work trip". Meanwhile, Moira's lawyer, Jean, tells Thea that dating Roy, a known criminal, is hurting her mother's case.

Oliver discovers Vertigo in Diggle's blood and realizes The Count has broken out of prison and is once again distributing his drug. Meanwhile, Moira goes on trial for her participation in the Undertaking. ADA Adam Donner collapses in court with Vertigo symptoms, so Laurel must step in and try the case against Moira. Oliver is torn between standing by his family during the trial and catching Count Vertigo. However, things change when Felicity follows a lead and walks straight into a trap set by Count Vertigo.

A robbery brings Central City police scientist Barry Allen to town. Citing a similar case back home, Barry offers to help Oliver and team with the investigation. Oliver senses there is more to Barry than meets the eye, but he's distracted by the similarities between this current case and something that happened on the island. Meanwhile, Felicity takes a liking to Barry, which doesn't go unnoticed by Oliver. Sin asks Roy for help when a friend of hers goes missing. 

After a fight with Cyrus Gold AKA the Acolyte, 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 Quentin to look into Cyrus, but when the stakeout on Cyrus goes bad, someone is killed. Roy is captured and tortured by Brother Blood.

Oliver must tackle a new threat to the city when bombs start to go off in Starling City. Felicity discovers the person setting them off is a man who goes by the nickname Shrapnel. The 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. Meanwhile, Roy continues to hide his new strength from Thea. Laurel's suspicions about Sebastian grow stronger. After Donner refuses to help her investigate, she turns to the Arrow for help.

Oliver is 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. 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.

If this reaction is blocked, you can find a version of it here.

The Arrow offers to train Roy so he can learn to control his enhanced strength. However, Roy is a rebellious student and refuses to listen unless The Arrow reveals his true identity, which Oliver declines to do. Meanwhile, Bronze Tiger escapes from prison and steals the Markov Device 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. 

As Laurel continues to unravel, Oliver and Quentin try to convince Sara to stay in Starling City and finally reunite with Laurel and Dinah. However, Sara's fellow League of Assassins member, Nyssa, 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.

Oliver brings Sara into Team Arrow. 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, 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. Meanwhile, Oliver throws Sara a welcome home party, but Laurel refuses to attend. 

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, 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.

While Oliver prepares for battle with Slade, Lyla asks Diggle to go on a mission alongside the Suicide Squad, a team assembled by Amanda Waller to undertake high-risk missions, even though the team includes Diggle's nemesis, Deadshot, and old enemies Bronze Tiger and Shrapnel.

When Frank Bertinelli is arrested, Oliver knows it's only a matter of time before his daughter, Helena, AKA The Huntress, returns to town. To make matters worse, Laurel is picked to try Frank's case, putting her right in the path of Helena. 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.

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.

Oliver, Sara, 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. 

The Mirakuru sends Roy into an uncontrollable rage and he unleashes 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 break through to Roy, so she goes on camera at Moira's campaign rally to lure him to Verdant. 

After Slade threatens to take everything Oliver loves away, 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.

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.

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, when Slade kidnaps someone close to Oliver's heart, Oliver is pushed to the edge 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.

My thoughts on season 2 of Arrow.