Chicago Med went through a cast shakeup at the end of Season 4, although you wouldn't know it just based on the events of the season finale. News broke that actors Colin Donnell and Norma Kuhling would depart Med as regulars ahead of Season 5, but the episode didn't give them any closure.
In fact, it ended on a cliffhanger for both characters that begged the question: how would Med finish their storylines without the actors on board? Well, now we have at least half an answer. Colin Donnell is coming back as Connor, but what about Ava?
Well, first things first: Colin Donnell isn't returning as a regular, or even as a recurring actor. Us Weekly reports that Donnell is only on board for the Season 5 premiere, which will allow Chicago Med to give the character an actual exit on screen. The news of his departure in the first place came as a shock, and it almost didn't feel real until Donnell himself confirmed it. Connor was a huge part of Med from the very first season, and he had some big stories in Season 4, often with Ava.
The big cliffhanger at the end of Season 4 for Connor involved Ava, which makes it hard to imagine Chicago Med satisfactorily sending him off without featuring her as well, but there's been no news about Norma Kuhling reprising her role for the Season 5 premiere. There are ways for the show to just explain what happened off-screen over hiatus that could believably require Ava to be far from Chicago. Med could do it without Ava; should Med do it without Ava?
Ava was established as quite manipulative in Season 4, as the plot somehow thickened even after she slept with Connor's dad to secure funding and then set son against father. She may or may not have deliberately exposed herself to HIV+ blood, which felt pretty unrealistic up until the hints of Season 4's last couple of episodes showed a darker side of Ava.
In the penultimate episode of Season 4, Connor learned some upsetting information: his dad had died, and Ava seemed at first like a totally normal friend who wanted to help Connor in his tough time. The trailer for the finale, however, revealed that somebody at the hospital had killed Cornelius Rhodes with an overdose of insulin. Then, in the finale, things got super creepy.
At the end of the episode, Ava told Connor that, with his dad out of the picture, they could finally be together. Understandably, Connor rejected Ava's advances after she kinda sorta hinted that she'd knocked off his father for the sake of their "romance." Angry at the rejection, Ava called Connor an "ungrateful prick" and told him to "rot in Hell." She walked away, leaving Connor and viewers without any definitive answers.
I came up with a bunch of ways Chicago Med could explain Connor and Ava's absences after the finale, with my personal favorite being that Connor went on a mad vigilante quest to bring the murderous Ava to justice, but the best way to wrap everything up is probably to bring both Colin Donnell and Norma Kuhling back. Med is bringing back one; my fingers are crossed that Med brings back the other as well.
Jon Seda reportedly isn't returning to Chicago P.D., but his story didn't end on a cliffhanger. P.D. can get away with just removing Antonio Dawson. I'm not sure Med could pull it off with Ava. Find out when Chicago Med premieres its fifth season on Wednesday, September 25 at 9 p.m. ET, between the season premieres of Chicago Fire at 8 p.m. ET and Chicago P.D. at 10 p.m. ET.