'Chicago Fire' season 5 spoilers, plot news: someone from Antonio's past returns; Casey and Dawson fight for Louie

"Chicago Fire" season 5 is currently on a hiatus, but will be back next year with some explosive episodes, one of which caters to a surprising return.

America Olivo will be back to reprise her role as Antonio's (Jon Seda) ex-wife, Laura, in episode 12 of the current season. The character first appeared in "Chicago P.D."

It is unclear as to what brings Laura back into the fold. Interestingly, "Chicago Fire" is where paramedic Sylvie Brett (Kara Killmer), whom Antonio is currently dating, appears.

There is no word if the characters will meet in "Chicago Fire" season 5. It is safe to say that Antonio, who was part of the recent "Chicago Fire" season 5 episodes, will be there.

As fans know, Seda, who has been a series regular in "Chicago P.D.," is moving to the spinoff, "Chicago Justice." He will still be around though, thanks to crossovers in the "Chicago" universe.

In other news, the "Chicago Fire" season 5 dropped a bomb on Casey (Jesse Spencer) and Dawson (Monica Raymund) as they filed to be parents of Louie after they tied the knot.

However, his birth father enters the scene, making it difficult for the couple to co-adopt him. Showrunner Derek Haas teased in a The Hollywood Reporter interview that it will 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," he explained.

"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," he went on to say.

"Chicago Fire" season 5 will be back on Tuesday, Jan. 3, 2017, on NBC.