The third season of "Chicago Fire" ended on a high note, which means that a lot of exciting events are going to take place when the action-packed drama series returns to NBC for its fourth season.  

Season 3 concluded with Lieutenant Matthew Casey's (Jesse Spencer) life in peril, after he decided to go undercover to look into the suspected human trafficking operation of Jack Nesbitt (Eric Manius). Gabriela "Gabby" Dawson (Monica Raymund) discovered that Casey is missing, and the lifeless body of stripper Katya was lying on his apartment floor, just when Dawson was about to tell him that she is pregnant with their baby. 

During his interview with TV Line, executive producer Matt Olmstead shared a little teaser about the firefighter's fate, saying that Casey could either be kidnapped, framed for Katya's murder, or both, and fans will see it when the show returns next season.

Olmstead also talked about Dawson's surprise pregnancy, which could cause a major change for the character once the series resumes for the fifth season. According to the producer, Dawson cannot continue doing her job as a firefighter because of her condition. 

"It's interesting, because they can't be a firefighter. They'll fall back to Ambo. The alternative is getting a desk job in the fire department while you're still pregnant. So of the many things she's dealing with is the fact that she'd have to be reassigned off the truck," Olmstead said. 

Also, the executive producer revealed that the crossover relationship between "Chicago Fire" paramedic Sylvie Brett and "Chicago P.D." police officer Sean Roman (Brian Geraghty) will push through when the two shows return later this year. 

"We started looking at P.D. where we have the Roman character who had an ex-girlfriend, so then he's available. Then we were like, what would that be like? The possibility of the chemistry really jumped out at us and so that's where we wanted to go. It's a button within the finale and we'll see where it goes next season," he explained.

"Chicago Fire" season 5 will reportedly air in November.