Chicago Fire Boss on That Surprising Romantic Reunion in the Winter Finale: 'The Door's Open'

Warning: This article contains spoilers about Wednesday’s winter finale of Chicago Fire, titled “Best Friend Magic.”

There’s hope for Dawsey fans yet!

The season 8 winter finale of Chicago Fire promised a guest appearance by former original cast member Monica Raymund and, thus, an inevitable reunion between Gabriela Dawson and her ex-husband Matt Casey (Jesse Spencer). But that reunion went in a decidedly different — and much more romantic! — direction than many might’ve expected.

Early in the episode, Casey spotted Dawson, who moved to Puerto Rico at the end of season 6, admiring the “sacred ground” where Firehouse 51 had erected a small statue to honor Brian “Otis” Zvonecek (original cast member Yuriy Sardarov), who had died in the season premiere. Just as Dawson was about to explain the reason for her short, two-day visit, Casey was sent on a call. But when he returned, they connected, and it was clear there were, as Dawson said, “a lot of feelings wrapped up here.”

She also invited Casey to a fundraiser for the relief organization for which she was working, and then provided an opportunity for them to dress up, dance a little, and … oh my goodness, did they really just have sex?!

“I never felt I got good closure with the two of them — not even that this is closure,” showrunner and executive producer Derek Haas tells PEOPLE. “It’s actually more of like an opening. But I didn’t feel like I had told the end of their story back when we started season 7.”

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The episode ends with Dawson leaving Casey a voicemail before she leaves town saying she had a great night and that he was welcome to visit her any time, thus ushering in a Dawsey 2.0.

“I love the scene in the hallway where Casey’s walking out of Dawson’s room and it’s not like he’s sneaking away like a thief in the night or anything,” Haas says. “He’s made a choice in the moment, the night before, to say that this was not a mistake. And this isn’t a mistake. This is what he wants. He leaves with this little half-smile on his face as he’s walking down the hallway. … They were clear-eyed that she was only going to be there for a weekend.”

“I love leaving it open-ended,” Haas adds. “This is the one true love of both of their lives to this point. And the door’s open — or the tent flap is open, I should say.”

In the latter half of season 7 and much of season 8 thus far, Casey has had a slow-burn flirtation with Dawson’s good friend and fellow paramedic Sylvie Brett (Kara Killmer). And while nothing has happened between them so far, Sylvie will surely have mixed feelings if and when she finds out about Dawson and Casey’s night together.

“Brett is the type of person, and I think this is well established over the six seasons she’s been on the show, she’s the type of person who will suppress her own feelings if she thinks that somebody else’s happiness will be achieved by her pushing down her own feelings,” Haas says. “And I think that’s part of what this weekend was. You see it when she’s talking to Foster after she asked Casey how his weekend was. He was like, ‘It was great,’ and she’s like, ‘Oh, I’m so, so glad to hear that.’ Foster picks up on that. But that’s Brett for you. But I will add, she, more than anyone, had the best seat in the house for the Dawson-Casey relationship and watched it through all of its trials and tribulations. So I think she realizes there are feelings there that are beyond distance and an ocean between them.”

And that, Haas says, “will certainly affect” Casey and Brett’s relationship going forward.

“You’re going to see a chance for Casey and Brett’s friendship to grow past even where it is now in the second half of the season,” Haas teases. “But this weekend will definitely be a subject of conversation.”

RELATED: Chicago Fire‘s Yuriy Sardarov Speaks Out About His Departure: ‘The Greatest 7 Years of My Life’

Of course, romance wasn’t the only thing on the menu in the midseason finale. After all, Kelly Severide (Taylor Kinney) had the big cliffhanger moment. He’s alone in a basement with an arsonist, a flare, and a whole bunch of flammable chemicals when the episode fades to black.

“We’ve done arsonists on the show before, but typically they have mental problems,” Haas says, revealing that the next episode will pick up one second later. “I thought what might be more dangerous and more formidable is if the arsonist is a contract arsonist, like a criminal for hire who doesn’t really give a s— who he destroys. … Severide is not a guy who’s afraid to throw down, and as he said earlier this season, he doesn’t get nervous. So you’ve got a career criminal and you’ve got Severide and you’ve got a flare and you’ve got flaming chemicals and you’ve got five people above them. Yeah, that’s about to happen.”

Chicago Fire returns Jan. 8 at 9 p.m. ET/PT on NBC.