While most television shows have already debuted their newest seasons, 'Chicago Fire'" is trailing behind, with a week-and-a-half to go before its Season four premiere.

The first episode of the season, 'Let It Burn' will be an explosive and action-packed episode. Viewers will finally learn what had happened to Casey after his undercover operation led him to a very dangerous territory. While Casey survives the kidnapping, it seems that he will be affected by the harrowing ordeal and will be left with some trauma, reports TVLine.

Casey struggles to deal with the aftermath of his actions, given "what he had to do to survive that ordeal, which would haunt a lot of people. He had to punch his way out," executive producer Matt Olmstead, revealed.

To complicate matters further, Casey learns that the case against Nesbitt won't go forward due to the involvement of cops, among other complications. Casey refuses to accept that everything he had gone through, including witnessing an innocent girl die, was all for naught. Olmstead added, "Voight advises him not to do what he thinks he's going to do, and Casey is hellbent." 

Given Casey's trauma, Dawson puts off telling him about her pregnancy. However, once she reveals the news, Casey is given some perspective. Now that he has a baby on the way, it will help distance him from what he has gone through.

Entertainment Weekly reports that Severide will also have to deal with some bad news of his own. Due to the high turnover rate on his squad, his leadership abilities have been questioned and thus, he will be stripped of his rank. Severide gets a rude awakening when he realizes that he will be replaced by Captain Dallas Patterson (guest star Brian White).

Meanwhile, new candidate, Jimmy Borelli (Steve R. McQueen) is also set to cause some trouble. He makes a horrible first impression after his brother drops him off duct-taped and late on his first day at Firehouse 51. Chief Boden is very displeased and sends him home.

Fortunately, not everyone will take to disliking the new candidate. It has been revealed that Brett and Chili, from the ambo, will be vying for his attention.

"There's a rivalry between Chili and Brett for his affection, and being friends, one of them defers to the other and fairly quickly we get a nice romance going with Brett or Chili," Olmstead also revealed.

'Chicago Fire' Season 4 debuts on Oct. 13, at 10 p.m. ET on NBC.