Felicity and Diggle head to Lian Yu to look for Oliver; Isabel Rochev (Summer Glau) prepares a hostile takeover of Queen Consolidated; Roy tries to fill the Arrow's absence.
Oliver discovers that thieves are hijacking medicine being sent to Glades Memorial; Roy is arrested after attempting to stop the thieves; Laurel plans to catch the Arrow.
A criminal once put away by Lance breaks out of prison and returns to his old ways of torturing and killing women; the district attorney seeks the death penalty for Moira.
Oliver learns that a man is transporting illegal guns into the Glades; Felicity shares stunning information with Oliver; Donner asks Laurel out.
After Oliver and the Canary are attacked by a trained killer at the Queen Mansion, the Canary confesses where she's from; Moria must choose whether to plead guilty to murder and conspiracy or take her chances in court.
Amanda Waller tells Diggle that Lyla went missing after pursuing a lead on Deadshot in Russia; Moira's lawyer thinks Thea's relationship with Roy, a known criminal, is hurting Moira's case.
A mysterious illness impacts hundreds of people in the city, including Diggle; Oliver realizes The Count (Seth Gabel) has escaped from prison.
Central City police scientist Barry Allan investigates a seemingly impossible robbery; Sin turns to Roy for help when a friend goes missing.
Oliver is drugged and left for dead after a fight with Cyrus Gold; Felicity and Barry grow closer; Brother Blood captures Roy.
Arrow tries to stop a man from setting off a bomb at a rally but gets trapped in the process; Thea witnesses Roy's superstrength and demands answers.
Oliver feels conflicted when Laurel asks the Arrow for help investigating Sebastian Blood; Sin wants Roy to test his new super-strength.
Arrow offers to train Roy, but Roy refuses unless Arrow reveals his true identity; Malcolm's earthquake machine is stolen by the Bronze Tiger; Laurel spins out of control after she is disbarred.
Lance and Oliver try to talk Sara into reuniting with Laurel, who continues to unravel; Dinah is kidnapped.
Felicity feels left out when Oliver makes Sara a part of the team; a brilliant thief known as The Clock King arms himself with technology that can open bank vaults; Laurel refuses to attend a party for Sara.
Oliver is stunned when he discovers that Slade is in Starling City; back on the island, Sara and Oliver form a plan to deal with Slade's growing Mirakuru-induced rage.
Oliver prepares for battle with his former friend Slade; Amanda recruits Diggle to stop a warlord, but he is surprised when he meets the rest of the team she has assembled.
Oliver expects the Huntress (Jessica De Gouw) to return once her father (Jeffrey Nordling) is arrested; Laurel is involved in a hostage situation at the courthouse; Roy tries to keep Thea safe.
The repercussions are massive when Slade makes a move against Oliver; a key player in Oliver's team starts to question his decisions.
An epic battle ensues when the team find Slade waiting for them in the lair; Thea reaches her breaking point; Laurel struggles with a secret.
When the mirakuru sends Roy into a blind rage, Oliver must find a way to stop him; Thea tries to lure Roy in by going on camera at Moira's campaign.
Diggle and Felicity go to extremes to keep Oliver from surrendering to Slade; Thea thinks about leaving town; Laurel goes after Sebastian Blood again.
As Slade's soldiers target the city, Oliver rallies his team; Felicity receives game-changing news from S.T.A.R. Labs; Thea and her father come face to face.