Chicago Fire : Season 4

Casey is placed in a dangerous situation while working undercover to bring down a trafficking ring being run out of Nesbitt's club. The squad's high turnover rate results in an unwelcome surprise for Severide. Dawson recognizes that her life is about to change. A new candidate makes an unusual first impression. Residents band together to protest a drug den in their neighborhood.

Boden's job is on the line pending an internal investigation. Severide adjusts to Patterson, his new commanding officer. Dawson shakes things up at the work. Casey searches for important evidence in his investigation of Nesbitt. Herrmann tries to keep the peace with Molly's new neighbors.

Boden offers to host a wedding at the firehouse after a fire ruins the ceremony, but Chief Riddle is against it and his political aspirations cause friction among the firefighters.

Chief Boden finds himself in the middle of a fiasco concerning a female neighbor, who he believes is setting him up. Severide, who is still on probation from his altercation with Captain Patterson, receives a surprise visit from his father and discovers some interesting information on Patterson that could be a game changer. Meanwhile, romance blossoms at the Chicago Fire Department gala.

Chief Boden confronts Maddox, believing he is the hand behind Serena's accusations intended to skew Boden's credibility from the approaching trial. Severide reaches out to Jamie, Maddox's lawyer, in an effort to help out and Capt. Patterson questions Boden's ability to remain Chief. Meanwhile, Brett and Chili discover a man passed out in a garden that may have a connection to a call from a previous crash site and Otis looks to fill up his social calendar, but the situation hits a bump in the roa

Patterson replaces Boden as chief. Dawson becomes a target of the conspiracy. An act of violence will change 51 forever.

Herrmann fights for his life after being stabbed; Cruz hits the streets to find Freddie; Mouch proposes to Trudy. (Malignant (1) aired on Chicago Med, season 1, episode 5. Now I'm God (3) aired on Chicago P.D., season 3, episode 10.)

A tornado threatens Chicago. Chili makes a major mistake, which causes Brett to report her to Boden. Otis asks Dawson to help him solve his women troubles. Severide assists a Department of Homeland Security agent.

Freddie's father begs Herrmann to forgive his son's assault. Casey discovers that a makeshift shelter housing people displaced by the tornado may close. Casey attends a fund-raiser at the request of an alderman. Dawson and Brett experience repercussions after telling Boden about Chili's erratic behavior.

The firehouse is on high alert when mysterious threats begin to emerge throughout Chicago. The situation turns dire when news of a mass shooting brings members of squad and truck into the middle of a dangerous and harrowing scene. Lt. Casey works diligently to investigate the missing money from the fundraiser for the victims of the recent tornado. Meanwhile, Jimmy agrees to represent the firehouse in the first annual "Battle of the Badges" boxing match against the 21st district police department

Lt. Severide confronts Chili about his suspicions regarding her erratic behavior, but she doesn't take too kindly to his intentions. Members of the firehouse rally around Casey, who they believe is a perfect candidate to run for the position as Alderman. Jimmy faces off against Antonio in the first annual "Battle of the Badges" boxing match.

Firehouse 51 responds to an odd call from a neighboring firehouse and the unusual circumstances prompt Severide and Cruz to take the investigation into their own hands to search out the real story. The truck welcomes new firefighter Stella Kidd, but her addition has repercussion inside the firehouse. Casey moves forward in his run for alderman, but begins to realize that some voters have their own personal agendas for wanting him elected.

Casey continues his run for alderman, but a citywide propaganda attack against his campaign makes him reconsider his candidacy. The rescue squad is summoned to the scene of a man trapped inside of a burning car with suspicious evidence suggesting that that the fire may have been intentionally set. Mouch's upcoming bachelor party looms, but with Trudy's nerdy brother Larry handling the details, everyone fears for the worst. Meanwhile, Jimmy and Brett take a kidnapping investigation into their own

Severide and Cruz find a child's remains inside a chimney while investigating a possible carbon monoxide leak inside a home. In other events, Casey braces for the worst in his run for alderman while Alderman Becks continues to bad mouth him to the press.

Sylvie witnesses a murder and is threatened by the shooter not to go to the police. Firehouse 51 jumps into action when a fire breaks out at a restaurant and traps several people inside a vault. Mouch starts to get cold feet.

The team responds to a building collapse that's trapped more than a dozen people. Dawson's quest to foster Louie is aided by a familiar face. Otis, who's on medical leave, meets his temporary replacement. Severide and Kidd continue to see each other. Casey is at odds with Antonio.

In the Season 4 finale, Boden and Jimmy are at odds. Kidd deals with her unstable ex. Dawson continues her quest to foster Louie. Casey's new political consultant urges him to think big. The team responds to a dangerous structure fire.