Killmer says “the door’s open” for a future Sylvie return.

Who’s ready for a wedding?

For Chicago Fire fans, the upcoming Brettsey nuptials are both exciting and sad, because the episode will mark Kara Killmer’s last. Killmer joined the show in season 3 as EMT Sylvie Brett, and in her final episode, she’ll experience a full-circle moment when she gets to marry Matt Casey (Jesse Spencer).

“I’m selfishly delighted that she started her journey in Chicago when she was left at the altar by her high school boyfriend, and I love that she ends up across the aisle from the love of her life and the most eligible bachelor in Chicago and Portland,” Killer tells EW. “It’s very much the natural end for the arc of her character. So she does wind up with everything that she always wanted.”

But that’s not to say that the wedding will go off without a hitch. For one thing, it’s happening in a fish store thanks to Tony’s (Anthony Ferraris) screw up. “Sylvie is a little bit like Monica Geller. She’s very organized and very particular, so it’s sort of perfectly comical that she winds up in this situation,” Killmer says.

And yet, this is kind of what Firehouse 51 does. “This is a staple of our show where one character has a massive problem that the rest of 51 wants to come together and create a solution that’s even better than what you could have imagined,” Killmer says. “So it’s sort of one of those situations, but it’s comical.”

By the time the team is done with the place, it’s worthy of a wedding. “They really transformed it,” Killmer says. “I told the owner of Tank It Easy, which is the real name of the aquarium, I was like, ‘You’re going to have to prepare because people are going to want to get married here after this.’”

For Killmer, at the end of the day, it was a good farewell. “My very last day we shot the reception, so I got to finish my entire filming journey with a gigantic party and some cake. So I was satisfied.”

But is the door closed for good on Sylvie? After all, Spencer exited the show years ago and he’s already been back a handful of times. “The door’s open for me,” Killmer says. “I’m happy to come in anytime they want to bring me back. 51 has a unique way of getting itself into trouble, and if they need Sylvie to come through and tell ’em what’s what, I will be there.”