[Warning: This post contains spoilers from Chicago Med's Season 4 premiere. Read at your own risk.]

It's official: Chicago Med has lost a member. The Season 4 premiere saw Sarah Reese (Rachel DiPillo) exit the hospital after a major fallout with her former mentor, Dr. Charles (Oliver Platt).

It all went down when Sarah's biological father collapsed after Charles accused him of being a serial killer and Charles hesitated before calling for help--an act Sarah just couldn't forgive. Unable to be in the same room with him, let alone hospital, Sarah decided to leave her residency, effectively ending her time on the show. And in case you're holding out hope that you'll see her again soon, showrunners Andrew Schneider and Diane Frolov say don't count on it.

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"We may bring her back — Rachel is a wonderful actor and Sarah is a great character — but at this point, we don't have definite plans," they told TV Guide.

For someone like Charles, who rarely opens up on the level that he did with Sarah, losing someone so close to him is a huge deal and that loss will continue to weigh on him as the season progresses. "His relationship with Sarah was very important to him. [Their falling out] is gonna affect how he approaches medical students going forward," said Oliver Platt. This doesn't bode well for newbie interns Else Curry (Molly Bernard) and Terry McNeal (Colby Lewis) who will need some guidance while learning the ins and outs of the ED.

Elsewhere, Rhodes (Colin Donnell) had a huge decision to make after receiving the offer of a lifetime to join the prestigious Mayo Clinic in Minnesota. Not one to let him go without a fight, Bekker (Norma Kuhling) went to great lengths to make him stay including getting a group of investors to fund his high-tech experimental program in the ED. While we don't know what exactly she did to convince them to donate funds, it looks like that dinner with Rhodes' father will create some problems down the road.

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"What she did will have profound effects on her relationship with Connor," Frolov and Schneider teased.

But Bekker and Rhodes aren't the only ones getting put through the ringer this season. Ethan (Brian Tee) and April (Yaya DaCosta) will still be at odds over Ethan's sister Emily (Arden Cho), who remains very much in the picture now that she's pregnant. "They're gonna continue to have a lot of problems with Emily, that's gonna be a big source of conflict." Buckle up, things are about to get bumpy between these two!

Meanwhile, Will (Nick Gehlfuss) and Natalie (Torrey DeVitto) will have their own problems to overcome. Natalie may have accepted Will's proposal (yay!) but she might not be that excited about going through the whole wedding process a second time, something that won't sit right with Will who's never been married.

""You just see a lot of personal conflicts coming up because Natalie has been married before. Also, her husband died and so there's a little bit of worry doing that again," Torrey Devitto explained.

Plus, there's the whole issue of their very different backgrounds which inevitably makes wedding planning all the more difficult. "He grew up in a very religious Catholic family. Natalie did not. So she didn't take that into account, that he would want a big religious wedding. He has a bigger family, she has a smaller family. So there's just a lot of things that they're learning about each other, which makes him feel like maybe she's not so invested," she added.

Fasten your seatbelts, there's going to be some serious drama this season!

Chicago Med airs Wednesdays at 8/7c on NBC.

Rachel DiPillo, Chicago MedRachel DiPillo, Chicago Med