After Ronnie attacks a physicist, Barry and the team realize they need to go after Caitlin’s fiancé who is now a dangerous meta-human. Barry struggles to balance his duties as The Flash and his relationship with Linda Park. Joe enlists Cisco’s help to reinvestigate the murder of Nora Allen. General Eiling returns to Central City.
When clues in a murder implicate Castle and Beckett’s nemesis, Dr. Kelly Nieman, Castle is called in to consult on the case.
As his troubles escalate to a boiling point, Jimmy finds himself in dire straits. An act of carelessness puts Chuck at risk.
Jimmy works his magic in the courtroom. Unexpected inspiration leads him to an unconventional pursuit of potential clients.
When the partnership between Ellis and Maya reaches a boiling point, Marty devises a plan that Jeannie opposes. Clyde develops feelings for Kelsey as they seek investors for their start-up.
Harvard ethics professor Henry Gerard seeks Harvey’s help with a case that requires a lack of ethics to win. Mike, meanwhile, does his best to not be spotted by the professor, whose class he never took; and Louis tries to wine and dine a socialite CEO.
Bellamy and Lincoln’s attempt to sneak into Mount Weather has brutal consequences. Abby fights to stay in control as Clarke steps up in her new leadership role. Meanwhile, with Monty and Harper still missing, a desperate Jasper confronts President Wallace and demands answers.
Phil starts to feel the teenage cold shoulder from Luke and, with Andy hanging around a lot as his apprentice, he easily steps in as his new right hand man. Gloria and the doctors suspect that Joe might be allergic to Stella. Mitchell does some freelance legal work at Jay’s closet company and working with Claire becomes a very enlightening experience for the both of them.
Upon learning that Aunt Edie has passed away, the Hecks board a train to South Dakota to take her to her final resting place.
Jane takes extreme measures as the team tries to apprehend a deadly gang of armored car robbers before their desperation to remain free costs more innocent people their lives.