"Chicago Fire" is gearing up for its fourth season, and the premiere will see Casey (Jesse Spencer) going undercover, Severide (Taylor Kinney) suffering a setback in his career, and Dawson (Monica Raymund) realizing that her life is about to change.

Here is the synopsis for the season 4 premiere titled "Let It Burn":

"In the season 4 premiere, Casey is placed in a dangerous situation while working undercover to bring down a trafficking ring being run outside of Nesbitt's club, and the squad's high turnover rate results in an unwelcome surprise for Severide. In other events, Dawson recognizes that her life is about to change; a new candidate makes an unusual first impression, and residents band together to protest a drug den in their neighborhood."

Back in season 3, Casey was kidnapped and a girl was shot in front of him. The new season will see him going undercover because the girl had tried to bring the bad guys down in the finale.

Speaking to TVLine, executive producer Matt Olmstead said that Casey's decision to go after the bad guys was fueled by the case's slow progress because "the feds are involved [and] there are complications, which sends Casey through the roof." The producer said that although Voight (Jason Beghe) will advise him not to do what he's planning to do, Casey will go ahead and try to end the operation in a bid to make sure that the girl didn't die in vain.

Meanwhile, it was revealed in the previous season that Dawson is pregnant with Casey's child. Because of her pregnancy, fans can expect that she won't be back on the truck but will likely be assigned somewhere else. She hasn't told Casey about the pregnancy yet, but Olmstead says that once Dawson lets him know about the baby, this will "pull him out of the quagmire that he's been in."

"Chicago Fire" season 4 premieres on Tuesday, Oct. 13 at 10 p.m. on NBC.