Slade returns and asks Oliver for help in tracking down his son. When they learn Joe has been taken hostage by mercenaries, their mission to save him gets complicated by a terrible revelation that could shatter Slade's hopes of reunion forever. Meanwhile, Vigilante reappears in Star City.

Sam and the girls go on a trip.

Grundy and Nygma become main attractions at Cherry's Place in The Narrows. Penguin wants revenge when he hears Nygma is mocking him on stage and enlists The Sirens for help. Meanwhile, Gordon is offered the position of GCPD Captain, putting him at odds with Bullock.

After a roller coaster car falls off the track at the county fair, the doctors at Grey Sloan tend to patients who spark memories about ghosts from their past. The series 300th episode!

When Annalise’s resolve to certify her class action lawsuit is tested, a surprising ally comes to her aid. Laurel and Michaela hit a roadblock after someone discovers their plans to take down Laurel’s father.

The Gladiators gather to celebrate Quinn and Charlie's wedding day; Cyrus, Mellie, and Jake deal with a new crisis in the Middle East.

While working on a case involving the ghost of a demented doctor, Sam and Dean get assistance from an unexpected source - Billie. Castiel finds his way back to the Winchesters.

Sheldon and Bert collaborate on a research project, despite Sheldon's embarrassment. Also, Penny and Bernadette coach Koothrappali on how to navigate his relationship with Ruchi.

Vanessa's past rushes back to confront her in an unexpected way; a secret is revealed that Doc has been protecting; in a bid to bolster his power, Dmitri sends Scab on an impossible mission.