Unthinkable

"Unthinkable" is the twenty-third and final episode of the second season of Arrow, and the forty-sixth episode overall. It aired on May 14, 2014.

Synopsis
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.

Plot
Oliver, Felicity and John are waiting for Roy to be cured. Oliver gives up saying the cure clearly doesn't work. However, Roy wakes up and fights with Oliver in an ambush by Slade's Mirakuru army. After leaving the clock tower, Diggle's girlfriend, Lyla Michaels blows up the clock tower, killing the Mirakuru enhanced men.

Thea then shoots Malcolm twice but he survives because he was wearing a kevlar vest. Malcolm tells Thea that he is proud of her for shooting him. He then tells her that Tommy had held a gun against him also but lacked the courage to shoot him. Thea, then gets a call from Roy who is completely cured. Roy tells her that he wants to meet her at his house, to which she agrees. Malcolm then tells Thea that Roy is one of the liars who should not be trusted. He tells her that he will be there for her when she needs him the most.

Meanwhile at the police headquarters, Quentin is busy rallying troops for the fight. He tells Laurel to stay safe. Laurel finds Sara with a stranger who makes her unconscious.

Meanwhile, Team Arrow and Lyla are then joined by Sara and the League of Assassins led by Nyssa. Sara then tells Oliver that she agreed to go back to the League in return for their help with fighting Slade.

Team Arrow and the League of Assassins go to Slade's headquarters where they fight but Slade manages to escape. Nyssa kills Isabel Rochev saying that Oliver has to start killing again to win.

Later, Thea meets Roy, who tells her that he has one last job to do, after which the two of them can start new lives together. While he is gone, Thea finds Roy's red bow and leaves him a note, telling him that the trusting Thea Queen is gone and she will never see him again.

Quentin rushes to Laurel who tells him about Nyssa. Meanwhile, one of Slade's followers attacks Quentin and kidnaps Laurel.

Quentin meets Team Arrow and tells Oliver that he respects the latter's non-killing promise. However, he tells Oliver that he should start killing again because Slade is a monster who needs to be put down for good. Oliver, while talking to Felicity, agrees that Slade is a monster and needs to be killed. Felicity, however, tells him that Oliver made a promise which he has to keep.

Diggle and Lyla meet up with the Suicide Squad, and tell them to attack without killing. Later, they meet up with Amanda Waller who orders a drone strike on Starling City.

Meanwhile, Oliver tells Felicity to stay in his old house because he loves her.

Then Team Arrow and the League engaged Slade's army and cures each one of them. Oliver then gets a call from Slade, Oliver told him his sick of his games but he tells him that he has the person Oliver loves most - Felicity.

Oliver goes to meet Slade, who says that he keeps his promises. Slade then tells Oliver to decide between Felicity and Laurel. Oliver asks Slade about his hallucinations about Shado. He tells Slade that Shado was a very kind and brave lady who would not approve of the monster Slade has transformed into. While distracting Slade, Felicity injects the cure into Slade, ridding him of the Mirakuru.

Flashbacks reveal that Oliver brought Felicity to Queen Mansion purposely with a plan to say a fake "I love you" to lure Slade in, who had been watching the bugged mansion ever since his first visit. Flashbacks also reveal that Oliver discovered one of the bugs after his mother's murder.

Slade and Oliver then fight, with Slade telling Oliver that there is only one possible outcome to this. Oliver would have to kill him to win. He says that Oliver will remain a murderer.

On the Amazo, Oliver and Sara are captured by Slade who is injecting the Mirakuru in various prisoners with little success. Around the same time, Anatoly Knyazev apologizes to Oliver, and launches a torpedo, which stops Slade from shooting Oliver. Oliver then tells Sara to escape and fights Slade, however she gets sucked out of a hull breach and Oliver presumes her to have drowned. After a huge fight, Oliver emerges victorious as Slade is trapped by falling debris. Slade tells Oliver that he will come after everyone Oliver loves - his sister, Laurel, his mother, enraging Oliver who puts an arrow through Slade's eye, assuming him to be dead.

In the end, Oliver uses one of his trick arrows to trap Slade.

Meanwhile, Diggle, Lyla and the Suicide Squad had reached Amanda, who tells Lyla to think about her baby, telling Diggle that he is going to become a father. Diggle tells Amanda to call off the attack but she remains adamant.

After trapping Slade, Oliver calls Amanda and tells her that he has Slade and she can stop the attack now. Amanda finally budges and stops the nuclear attack.

Meanwhile, Roy finds Thea's letter and is left heartbroken. Thea leaves Starling City with Malcolm in his limousine.

Sara says goodbye to her dad and sister, telling them that she is making her first real life decision. She gives Laurel her jacket, telling her that she will be back. Laurel says that she will be waiting for Sara's return. After Sara leaves, Laurel and Quentin are walking back when Quentin suddenly begins to stumble and cough up blood due to internal bleeding from his injury from the Mirakuru enhanced soldier. Laurel calls an ambulance to help.

Slade opens his eye to see Oliver who thanks Slade for teaching him to kill when he most needed it. Slade tells Oliver that he will be back and see his promise completed. Oliver says goodbye to Slade, telling him that the latter is locked away from the rest of the world so as to not do any harm.

Oliver then meets up with Diggle and Felicity, telling them that A.R.G.U.S' prison on Lian Yu is more secure than any other in the world. Diggle then leaves the two for a moment of privacy where Felicity praised Oliver's deception on Slade but confessed that for a moment she believed his feelings for her were real stating that he "really sold it". Oliver smiles then states "We both did". Then he asks Diggle about Lyla but Diggle diverts the topic, telling Oliver that it's not important. Oliver tells Diggle that he's flying back home. Felicity asks Oliver how he knows how to fly a plane if he was stranded on the island for 5 years.

It then flashes back to after the boat exploded, where Oliver wakes up to find himself in Hong Kong, where he is greeted by Amanda Waller.

Trivia

 * When Leaving the island at the end of the episode, Diggle refers to Slade's new prison as "Argus's Super Max." Super Max was the name of a long-in-development script by David Goyer which would have seen Green Arrow attempting to escape from a prison made for supervillains after being placed there for a crime he didn't commit. The movie would've seen cameos from several DC villains as inmates of the prison.

Production

 * Preparation ran from March 28 until April 7, 2014. Shooting ran from April 8 until April 17, 2014.