In the wake of a tragedy that hits too close to home for the crew of Firehouse 51, everyone struggles to move on, especially as a new candidate arrives to join their crew.
As Darden's death continues to take its toll on the guilt-stricken Severide, he is left struggling to balance his duty towards an injured victim with his own injury during a rescue mission.
Mills faces a difficult choice between his mother and his job. Casey finds himself in an uncomfortable position when he faces the prospect of reporting a crime that has a connection to a familiar face.
As Boden faces backlash over a decision he made during a call, Voight puts pressure on Casey to save his son. Shay confronts a face from her past, which brings up painful memories.
Severide continues to deal with the aftermath of his injury. Casey stands up to Voight, which leads to unforeseen repercussions.
As concerns arise as to Casey's ability to handle the job in light of his issues with Voight, Casey receives unexpected help from someone in Voight's own team.
Severide's medical condition threatens to come to light after an incident during a call requires the crew to take drug tests. Inspired by one of his missions, Casey makes a decision about his relationship with Hallie.
In the wake of a gruesome discovery, Mills questions his future as a firefighter. Dawson and Shay face trouble as they try to rescue an abused 6-year-old.
When an injury forces Jose Vargas to walk away from his job, Casey and Severide step in to stop him from taking drastic measures. Cruz faces a family crisis.
A number of firefighters face charges after an expensive necklace goes missing from a house they were called to. Cruz's desperation to save his brother pushes him to make a questionable decision.
Severide confides in Dawson about his injury. Cruz deals with the aftermath of Flaco's death. Casey confronts a complicated family situation that forces him to choose between his mother and sister.
Dawson makes a risky decision during a call. Severide comes clean to Boden. Casey struggles with a difficult request from his mother.
Boden is guilt stricken when Ernie is implicated in a man's death. Severide struggles with the decision of his surgery.
When Severide returns to the Firehouse, he is shocked to find a familiar face from his past. Casey continues to drift away from his sister.
As Dawson tries to help her brother with a case, she ends up making a decision that threatens her friendship with Casey. Whaley pushes Severide to reconcile with his former fiancée.
As Casey's family struggles to recover, Cruz's guilt over his past actions leads to a dangerous predicament. Shay hits an unexpected hurdle as she tries to be a mother to Clarice's baby.
An old conflict comes to the surface between Boden and Severide's father. Dawson learns an unsettling secret about Boden.
Tension rises as Mills questions the events that led to his father's death. Severide, his father, and Casey team up to investigate a string of diner fires.
When a difficult call leaves the crew reeling, internal strife complicates matters as one of Severide's decisions is questioned. The crew finds themselves in peril when drug dealers attack the Firehouse.
As Mills tries to deal with the resentment of his colleagues, Shay rushes to help a friend with a medical emergency.
Severide faces a serious accusation from a paramedic. Casey's life spins out of control when Voight returns.
Severide learns more about Tara's history. Mills and Dawson's relationship hits a snag after a secret is revealed about his mother.
Reeling from Hallie's death, Casey is forced to team up with an old enemy to investigate the fire that claimed her life.
The crew is left trying to navigate a tense situation after a call sends them to the Cook County jail. Mills and Dawson are forced to make a major decision about their relationship.