Spoilers ahead for Episode 21 of Chicago Med Season 4, called "Forever Hold Your Peace."
Only one episode is left before Chicago Med closes Season 4, and the finale promises to send off at least two major characters. Fans have had a while to prepare for the prospect of saying goodbye to Connor and Ava, but it won't happen without some heartache. Connor's dad died in "Forever Hold Your peace," seemingly due to his heart condition.
According to the trailer for the Season 4 finale, however, foul play is to blame for Cornelius' death, and somebody at the hospital may be the murderer. Take a look:
Apparently, it was not just Cornelius' heart condition that resulted in his death in "Forever Hold Your Peace." The episode didn't show what happened leading up to Cornelius beginning to flatline; he was already gone by the time Connor arrived at his room. Although Connor hurriedly took over compressions and tried to get all the nurses (and Ava) in the room to keep working on his dad, Ava said that he'd already been down for ten minutes before he showed up. She pronounced him dead.
Based on the trailer for the next episode, sometime before Connor arrived, somebody had overloaded Cornelius on insulin, killing him. According to the doctor in the promo, the person who delivered the overdose had to work at the hospital. There are plenty of suspects at this point, as Cornelius wasn't exactly the easiest patient ever to set foot in the hospital, and the only character we can confidently rule out is Connor.
The most obvious suspect for Cornelius' killer is Ava. In the trailer, she's seen telling Connor that she did all she could for his father, and she is the one who performed the initial surgery on his heart. Ava did also sleep with his dad, which understandably threw a wrench in their relationship. Connor even suspected that she exposed herself to HIV+ blood as part of a twisted attempt to get sympathy.
Throw in the fact that she was on the scene trying to revive -- or perhaps "revive" -- Cornelius, and there are reasons to suspect Ava as the killer. Chicago Med has to write out Norma Kuhling somehow. Revealing that she murdered Connor's dad would certainly give Med a way to explain Ava's departure! The episode description for the Season 4 finale does state that Ava will fight "to keep her relationship with Connor." She's an obvious suspect.
But is she too obvious? Chicago Med did such a thorough job of establishing Ava as somebody with a deeply manipulative side that it wouldn't be much of a twist if she's revealed as a killer. At this point, my crackpot theory is that the killer isn't a hospital employee at all. Crises happen at Med all the time, and surely something could have gone wrong enough that somebody could steal enough insulin to kill Cornelius, right?
Or it could be some hospital employee who just isn't Ava. Chicago Med doesn't have to go so far as to kill Ava off to write out Norma Kuhling, and Colin Donnell is leaving as well. At this point, just about anybody could be the killer. Find out who did the dirty deed in the Season 4 finale, which will also see Dr. Charlies and Caroline making plans, and Agent Lee letting Will know that his life could be in danger. Again.