Reunited with his sister, Oliver and Thea find themselves searching through a familiar maze of catacombs. Meanwhile, John and Lyla partner on a special ops mission.

Felicity learns something new about Oliver that shocks her. Meanwhile, Diggle asks Curtis to go undercover for ARGUS. Dinah works with an unlikely ally.

Oliver assembles a group of unlikely allies – Slade, Nyssa, Merlyn and Digger Harkness – to engage in an epic battle against Chase and his army.

Prometheus goes to extreme lengths to destroy Oliver. In flashbacks, Oliver’s violent tendencies come to a head in a confrontation with Anatoly.

Oliver gets closer to the truth about Prometheus. Meanwhile, Helix refuses to continue helping Felicity until she does a favor for them.

In flashbacks, Oliver and Talia kill an illegal drug merchant from Robert Queen’s list. Talia again presses Oliver to return home, but he chooses instead to help Anatoli kill Gregor….

During the S.T.A.R. Labs incident, CCPD undercover officer Tina Boland develops a sonic scream after watching her partner die at the hands of drug dealer Sean Sonus. In the present…

Dean refuses Sam’s efforts to help him battle the Devil, and then wakes up to find himself five years in the future, in a wasteland where Lucifer has begun his…