Chicago Fire Stars Ponder Casey and Brett's 'Simmering' Potential Romance

Chicago Fire Spoilers Casey/Brett

Chicago Fire‘s Brett is finally back where she belongs in this Wednesday’s episode (NBC, 9/8c) — and back to exploring her feelings for Casey?

After breaking off her engagement to Kyle and leaving Indiana behind, Brett’s return to Firehouse 51 brings up “mixed emotion[s] for her,” her portrayer Kara Killmer tells TVLine. “She’s really happy to be back, happy to be back with her family. But she’s recovering from yet another failed engagement.”

Of course, the homecoming will also bring about a reunion with a certain firefighter captain. That first interaction between the paramedic and Casey is “interesting,” showrunner Derek Haas teases. Leading man Jesse Spencer, meanwhile, describes the moment as a “good” one. “I mean, she’s a friend. She’s a good friend, and he’s happy to see her come back,” Spencer adds. “She’s a great medic, and they work well as a team. So I think it’s a very platonic welcoming [when you] see someone that you like come back to the firehouse.”

But one can’t ignore that there were some less-than-platonic vibes between the colleagues last season. The hints of a possible romance “kind of came out of the blue, which I kind of liked,” Spencer admits. “And as of yet, we still don’t know if that’s going to happen down the road. They’re toying with it. And if it does happen, I’m glad it’s going to be a long game. It’s not going to happen very quickly. But the two characters have immense respect for each other. They like each other professionally.”

Spencer is also enjoying the fact that the relationship is just “simmering under the surface,” he says. “It’s not like a big hoo-ha. If anything, it’s gonna be that friendship which blossoms into something.” And neither character wants to ruin that friendly bond, so “that’s why they’re being careful.” Plus, after a string of broken relationships on both their parts, “they don’t want to blow it again. They can’t blow it again! Casey can’t take it anymore!”

As for Brett, “she’s just gonna play it cool for a while,” Killmer previews. “She’s just gotten out of an engagement, and she doesn’t want to presume anything. I think she very much thinks that she doesn’t know how she feels about it and doesn’t know how he feels about it. So they’re just going to focus on their work — for now.”