A rogue black ops team led by Onyx breaks into Kord Industries and steals something lethal. Oliver struggles to connect with William so he reaches out to a surprising source for help.
Slade returns and asks Oliver for help tracking down his son; the rescue mission gets complicated by a terrible revelation that could shatter Slade's hopes of reunion; Vigilante reappears in Star City.
As Slade continues to uncover clues about his son's last few years, Oliver makes a big decision. Meanwhile, the Green Arrow leads the team into battle against "The Dragon," a villain who is stealing valuable tech in Star City.
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.