In his darkest place yet, Oliver wonders if he has failed at everything; Oliver lashes out at Felicity and William; a surprising visit from an old friend has Oliver questioning his next move.
Looking to expand his empire, Diaz meets with a group The Quadrant, a coalition of mafia families; after Oliver's recent decision, Felicity and Curtis double their efforts to build Helix Dynamics.
Oliver turns to an old friend to help battle Diaz. Meanwhile, Rene is out of the hospital but has a hard time re-adjusting to life as Wild Dog. Also, Lance discovers something shocking about Black Siren.
After surrendering to the police for being the Green Arrow, Oliver tries to survive in the prison while a new unknown vigilante emerges in the Star City.
Still in prison, Oliver faces his biggest challenge yet. Meanwhile, Felicity gets an intriguing offer, and Diggle asks Curtis to go undercover for ARGUS.
Oliver and Felicity each make drastic moves to find Diaz; the new Green Arrow swoops in when arsonists target Rene's community center; Dinah faces pressure from the mayor to capture the vigilante.
Felicity learns something new about Oliver that shocks her. Meanwhile, Diggle asks Curtis to go undercover for ARGUS. Dinah works with an unlikely ally.
Slabside becomes even more dangerous after a guard is murdered and everyone is a suspect. Felicity enlists help from a surprising source in her pursuit of Diaz, and Laurel flexes her muscles as the District Attorney.
Still trapped in each other's bodies, Oliver and Barry head to Gotham City with Supergirl to find out why their reality changed and cross paths with the mysterious Kate Kane.