'Chicago Fire' Co-Creator Talks Casey and Dawson's "Surprising" Decision, Severide's "Emotional Crisis"

"We wanted the 100th episode to have something truly special," co-creator Derek Haas tells THR about the couple's life-changing decision.
Matt Dinerstein/NBC

[Warning: This story contains spoilers from Tuesday's fall finale of Chicago Fire, "100."]

For its landmark 100th episode, Chicago Fire gave its loyal viewers something some thought might never happen: Casey (Jesse Spencer) and Dawson (Monica Raymund) officially tied the knot.

There was no white gown, no teary vows and no drawn-out walk down the aisle, but their short-and-sweet civil ceremony was still a jaw-dropping occasion given their up-and-down relationship status over the show's five-year history.

However, their celebration was cut short when they found the birth father of their foster son Louie waiting for them outside their house. He told them he was determined to get his son back right just as the screen cut to black and the credits began to roll.

Casey and Dawson weren't the only ones starting a new chapter. After having to go to Chicago Med for a work-related injury, Severide (Taylor Kinney) decided to become a bone marrow donor for a woman he's never met after learning he was a rare match.  

To get the scoop on why the timing was finally right for wedding bells, Casey and Dawson's "complication" with Louie's birth father and the "emotional ramifications" ahead for Severide, The Hollywood Reporter spoke with series co-creator Derek Haas.

Why was now the right time to have them finally tie the knot?

We wanted the 100th episode to have something truly special and something that's been building up and is obvious, yet surprising. And Dawson and Casey have been, since the last scene of the pilot, something we've been aiming toward. It's something we want; I don't even know if we want it more than the fans want it. We just love them together. This show — while it has a lot of surprises and there can be some sad events — it is, in our minds, a positive show and it is about family and the fact that these two have been … They need each other. They proved it over and over again. So I think for us, it was almost as much for us as anything. We wanted to write that scene and I'm thrilled with the way it turned out.

As writers, how concerned are you with losing that dramatic engine of putting them together and breaking them up?

I'm not worried about it because I feel like there are so many storylines to be told with their characters that have nothing to do with marital problems or marital strife. We've already covered a lot of that, as people who have lived together and not lived together. He's got this job as an alderman, she's back to being a paramedic. I'm not worried about it, but ask me again in two years.

You introduced another big obstacle for them at the end of the episode with the arrival of Louie's birth father. What does that mean for them going forward? How is this person going to try to get his son back and how will they deal with that?

It's going to be surprising. People are going to think they know where that story is going and then it's not going to go the direction you think it's going. But it is a complication. She is fiercely protective of Louie. Casey wants to be his dad also, and they are going to pull out all the stops and do whatever it takes to really protect Louie more than anything. They know what he's been through. They want stability for him and they love him and what would you do in that situation? That's how we tried to answer that.

What was the thinking behind bringing up this storyline for Severide and have him volunteer to donate bone marrow?

We've always looked for somebody to come along that can capture Severide's heart, so to speak, and be his equal onscreen from a character dynamic standpoint. We're going to see more of Anna, who's the woman in the hospital bed, and hopefully that's going to be a story that thrives in the second half of the season.

Is she going to become a potential love interest for him as well?

Yeah, she's going to be a possible love interest if we can get to the part of keeping her alive. (Laughs.) … The actress — I know you barely see her in the eighth episode — but she's fantastic and we're having a lot of great writing from the staff coming towards that storyline. The first eight episodes were definitely more Dawson and Casey-focused, so it's good for us to shift focus sometimes in terms of whose storyline is the A-story. In the second half of the season, it's going to be a little more focused on Severide.

Jeff Clarke (Jeff Hephner) warns Severide that he's going to be in a lot of pain for months. However, Severide has a very physically demanding job, so how will this decision affect his career?

[Writer] Michael Gilvary was a bone marrow donor and so he's been through it. It is incredibly painful, but it's not debilitating. You're in pain but you can do your job. It's like a couple of weeks out and then you're back in. So while it is, as Gilvary described it, one of the hardest things he's ever done, that's also so much something Severide would do for someone else.

The episode opens with him seeming a little lost and restless. What is behind this feeling he has?

In these 100 episodes, we have Severide pretty well-defined as a womanizer and fly-by-the-seat-of-his-pants when it comes to anything emotional. We thought, you know what? Let's let him have an emotional crisis of, 'What am I doing here? What's the point?' So much of what a firefighter does is: does a rescue, drops somebody off at the hospital and then they never hear from them again. So we wanted Severide to try something or want to do something selfless that has emotional ramifications.

Chicago Fire returns Tuesday, Jan. 3, 2017, at 9 p.m. on NBC.