The latter almost hooked up after Casey rescued Brett when a stalker caused her ambulance to crash, and they came together at her apartment that night. But then, after a passionate kiss, Brett turned to Casey and asked, “If Gabby came back and asked you to leave with her, would you go?” And when she didn’t hear the answer she wanted, she sent him packing. “Brett does have a lot of romantic baggage,” Killmer tells Parade.com in an exclusive interview. “She was left at the altar. She had a broken engagement with Kyle. And even with Antonio, they were never on the same page, and then he split. In terms of the conversation that she had with Casey, in terms of her feelings, I think she’s always had a sneaking suspicion that she would never compare to Gabby, and, therefore it was always easy to convince herself that there was nothing going on there.” Of course, men see things differently, and for Casey, according to Spencer, it isn’t black and white. It was Gabby who left him, not the other way around; the fact that he might still have residual feelings for his ex-wife feels reasonable. “Just because someone has moved on doesn’t mean that you don’t still have an affinity for them or that you can’t have a love for them,” Spencer tells Parade.com. “I think this could have been lost in translation a little bit, or not put forth so bluntly. The idea of Gabby walking into that room would’ve been hilarious. Actually, that would’ve made for some fantastic television, let me tell you," he joked. Interestingly, according to Killmer, Casey has himself to blame for Brett’s rejection of him. While the two have been dancing around their feelings for a couple of seasons now, they have still remained great friends, and Casey has been trying to build up Brett’s self-esteem. “Casey’s encouraged her to prioritize herself and her needs,” Killmer says. “What does she want and what does she deserve? And so, he actually made her feel worthy. So, when that moment came and she asked him [about Gabby], it’s actually the first sign that she is choosing to prioritize herself. She asks the question because she doesn’t want to be a consolation prize.” For now, Casey has decided to give Brett some space in hopes that they will eventually be able to move on and get their relationship back on track. But in the meantime, that doesn’t mean they can’t date other people. So, executive producer Derek Haas has introduced a possible new romance for each of them, and both meetings happened in Season 9, Episode 4, “Funny What Things Remind Us." First, Casey rescued an attractive woman trapped in a car named Sidney. She turned out to have a morbid sense of humor, which was strange, but funny and appealing enough that the two ended up going on a couple of dates. “He’s taken off guard,” Spencer says of meeting Sidney, who came to Firehouse 51 and gave him her business card. “This is awkward, because it comes out of nowhere. He said that he was going to give Brett some space, but what does that mean? Are they going to go out and start dating other people full-time? They are still around each other and trying to be friendly with each other, so it’s going to make it more complicated, I think, for the characters to do that. Not less complicated.” Of course, Casey didn’t call Sidney until after he saw Lieutenant Grainger and Brett together at Molly’s. Grainger works in a different firehouse, but his truck had come out as backup on the earlier call where Casey rescued Sidney. Grainger saw Brett in action and expressed an interest. “I think it’s a roadblock in every sense of the word,” Killmer says of the idea of dating Grainger. “Brett is trying to take space. She’s trying to get over her feelings about Casey and trying to move on. So, we have some serious angst coming your way.” That said, what will it take to finally get these two together? “It’s anyone’s guess,” Killmer admits. “I have ideas. Could it be a grand gesture? I don’t know. Maybe it would just be a really candid and heartfelt conversation because they attempt to communicate well with each other. But, there’s always the possibility that because of girl code, it doesn’t matter what he says. She’ll just be like, ‘Yeah, there is no ‘regardless of Gabby,’ period, no matter how much I love you.’ But I doubt it.” Chicago Fire airs Wednesdays at 9 p.m. ET/PT on NBC. Next, Joe Berlinger on bringing Elisa Lam to life in Crime Scene: The Vanishing at the Cecil Hotel 

Chicago Fire s Jesse Spencer   Kara Killmer on the Casey and Brett Romance - 83Chicago Fire s Jesse Spencer   Kara Killmer on the Casey and Brett Romance - 5