The story of firefighters in Chicago.
Cast: Jesse Spencer, Taylor Kinney, Monica Raymund, Lauren German, Charlie Barnett, Yuri Sardarov, Christian Stolte, Eamonn Walker, Anne Lockhart, David Eigenberg, Joe Minoso, Randy Flagler, Don Kress, William Smillie, Steve Piper, Teri Reeves, Mo Gallini, Nicole Forester, Kathleen Quinlan, Anita Nicole Brown
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; and the team responds to a dangerous structure fire.
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; and Casey is at odds with Antonio.
Dawson saves a young boy from an apartment fire; Kidd's idea for Molly's doesn't go as hoped; Severide hits a wall while advocating for new fire masks; and Cruz and Brett utilize a secret weapon to get Otis to see Dr. Halstead take a blood test.
Severide watches Holloway's young son while she testifies in court; the squad responds to a fire at an art gallery; Casey receives a suspicious package in the mail; and Brett confronts Otis, who isn't taking care of his important issues.
Casey becomes involved when a high-school student is the victim of a gang-retribution incident; Severide lends a hand to Det. Holloway, who's involved in an undercover operation, and watches her 9-year-old son at the firehouse; Brett and Jimmy are called to aid a woman who takes a liking to Jimmy; Otis makes a surprising discovery; and Herrmann's bar-running prowess is challenged.
Sylvie is threatened when she witnesses a murder.
Severide and Cruz discover the remains of a case that may be connected to a case Severide worked on years ago.
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.
Severide and Cruz take matters into their own hands when Firehouse 51 responds to a suspicious call from a neighboring firehouse.
Severide confronts Chili about her behavior, while Jimmy faces Antonio in the first annual "Battle of the Badges".
Mysterious threats begin to emerge throughout Chicago and the situation gets worse when news of a mass shooting brings Firehouse 51 into a dangerous scene.
Herrmann goes to court to testify against Freddie but when the perpetrators father reaches out to beg forgiveness for his sons malicious attack, a tormented Herrmann is left to figure out what to do. Following the aftermath of the recent tornado, Lt. Casey learns the makeshift shelter housing victims is on the brink of shutting down.
The city of Chicago braces for a tornado.
While a member of Firehouse 51 falls victim to a near-fatal stabbing, the other firefighters rescue a woman who attempted to commit suicide.
Clues to Serena's possible whereabouts are uncovered, while Captain Patterson has news for everyone.
Patterson confronts Boden about his ability to lead the firehouse.
Boden finds himself in the middle of a fiasco concerning a female neighbor he believes is setting him up.
Severide and Patterson's differences reach a boiling point, while a visitor from Cruz's past asks for a favor.
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.
A member of Firehouse 51 requires the support of the whole team to recover from a near disaster.
Boden's job is on the line as the crew of Firehouse 51 continues to search for evidence that could clear him of any wrongdoing.
Internal Affairs investigates Firehouse 51 following a complicated call to a fire.
Casey finds himself in dangerous territory at the center of an undercover operation to bring down a trafficking ring out of Nesbitt's strip club.