'Chicago Fire' season 5 spoilers: Arrival of Louie's father to be explored

After the much-awaited Dawsey wedding, fans will see more complications for the responders of Firehouse 51 when "Chicago Fire" season 5 returns next month.

On the show's 100th episode milestone, Casey (Jesse Spencer) and Dawson (Monica Raymund) finally got married after overcoming many challenges in their relationship. They tied the knot in a small courthouse ceremony that was witnessed by their closest colleagues and their adopted son, Louie. The episode also featured the responders toasting to the 100th anniversary of Molly's Bar.

Series creator Derek Haas recently caught up with TV Line, and he hinted that Casey and Dawson will find it difficult to deal with the arrival of Louie's biological father. Moving forward, viewers will have a clear picture of his true intentions and why he entered their lives.

"There's two things going on there. One, we didn't want it to just come out of the blue at the very end, because then it's like you didn't even give the audience a chance to guess what was coming. But I'm hoping over the next few episodes, your expectations of who this guy is — what he wants, what he's doing — are going to flip a few times," Haas said.

As for the back half of the season, Haas mentioned that there will be "bigger episodes coming." Similar to what they've done in the past, huge storylines will be explored, including a major complication that affects the entire firehouse.

"We're going to have a shocking ending around Episode 13 that's going to lead into 14, where 51 is never going to be the same," he told TV Guide. "And there's going to be a call that Casey goes on where he has to decide who he's going to save in a real Sophie's choice. And it's going to be haunting, but it's also going to have ramifications that take up the next episode," he added.

"Chicago Fire" season 5 returns on Tuesday, Jan. 10, at 10 p.m. ET on NBC.