Kidd and Severide's honeymoon is interrupted by a dangerous person from their past. Kidd's former academy classmate joins Firehouse 51. Brett and Violet reflect on their relationships.

Javi spends a couple of shifts at Firehouse 51. Kidd and Carver work together to help Carver's former boss. As Hawkins and Violet's relationship blossoms, Gallo turns his attention elsewhere.

Kidd recruits Carver, Capp and Tony to help prepare her new lieutenant's quarters. Severide and Det. Pryma pair up to work a police investigation. Firehouse 51 fights a movie theater fire.

Kidd gets a glimpse into Carver's chaotic personal life. Mouch and Herrmann receive an unexpected gift.

Firehouse 51 hosts a Halloween open house. Kidd and Severide help a young girl after she gets kicked out of her home.

Severide and Kidd investigate an explosion at a jewelry store. Cruz and Chloe take steps to make Javi a permanent part of their family. Gallo, Ritter and Mouch try to bond with Carver.

Herrmann is tasked with fulfilling a man's dying wish. Kidd reflects on her Girls on Fire program after one of her students graduates from the Fire Academy. A heckler harasses Firehouse 51.

Det. Pryma asks for Severide's help on a case involving explosives. Gallo and Carver clash after Gallo improvises on a call. Violet encourages Brett to start dating again.

Severide struggles with the cost of helping Det. Pryma with the Martucci case. Gallo campaigns for Herrmann to represent 51 at the National Firefighter’s Association’s Winter Conference. A familiar face makes a shocking return.

Det. Pryma's case comes to an explosive end with Kidd and Carver's lives in danger. Brett installs an infant safe surrender box at 51. Violet is determined to take Emma down.

Firehouse 51 prepares for their semi-annual firehouse inspection. Brett fights to save her paramedicine program. Commander Martin Pearce asks Severide for a favor.

Truck and Squad clash after a tense call rescuing a doomsday prepper. Herrmann struggles with Cindy's diagnosis. Violet gives Brett and Gallo dating advice.

Firehouse 51 helps Herrmann put on a school fundraiser. Carver's troubled brother comes to town. A grateful citizen is determined to thank Brett and Severide for saving his life.

An annoying floater takes a romantic interest in Violet. Ritter catches a local politician in a compromising position. Mouch and Severide help Trudy with an arson investigation.

Kidd, Seager and Carver investigate a fire at the city stables. Kylie clashes with some of the firefighters over changes due to budget cuts. Herrmann struggles to keep it together as Cindy's condition worsens.

Cruz feels the burden of his increased responsibilities. Kidd, Gallo and Carver get caught in the middle of a gang war on a call. Herrmann wrangles Trudy for help lifting Cindy's mood.

Mouch builds a classic firetruck model for the Deputy District Chief but needs some assistance from Gallo and Ritter. Brett and Violet encounter multiple victims with a strange set of symptoms. Cindy's chemotherapy results loom over the Herrmann family.

A familiar face returns to Firehouse 51 to serve with Kidd on a special task force. Mouch and Capp work to keep Tony safe, as he's days away from breaking the CFD's perfect attendance record. Old grudges resurface when Gallo reunites with a family member.

Boden, Ritter, Herrmann and Kidd work together to take down a local politician responsible for a chemical fire. After his aunt's accident, Gallo worries about their future.

Herrmann works on becoming a better man after Cindy's cancer journey. Kidd bonds with a homeless victim on a call. Kylie takes her firefighter exams. A harrowing call takes a toll on Brett.

Carver deals with the fallout of his arrest. Brett searches for closure with the baby she rescued. Capp weasels his way into the Firehouse 51 group chat.

Brett waits for life-changing news. Herrmann encounters a psychic with a grave warning on a call. Kidd finds a new lead on the Homeland Security case.

A new chief shakes things up at Firehouse 51. Violet and Novak work to uncover the truth behind a car crash. Cruz keeps a watchful eye on Severide and Damon's growing bond.

After Damon disobeys Kidd's orders on a call, he turns to Severide to protect him. Herrmann searches for the perfect scent to spice things up with Cindy.

Severide and Van Meter investigate a fire at a family-owned restaurant. Pascal questions Kidd's leadership.

Violet risks her job to deliver a baby on a tragic call. Mouch, Capp and Tony help Cruz track down Javi's stolen bike. Damon's departure weighs on Severide.

Kidd and Severide investigate a trucking company responsible for a string of accidents. Herrmann recruits Kylie to help get new radios. Firehouse 51 celebrates Violet's birthday. Carver's allegiances are torn.

Severide gets wrapped up in an Illinois State Police investigation after discovering illegal guns on a call. A bird harasses Mouch on the apparatus floor. Kidd keeps an eye on Carver.

Pascal and Severide revisit the storage facility fire in hopes of uncovering new evidence. Cruz helps Mouch take his studying to the next level. Novak prepares a proposal for Chief Robinson for a whole blood program.

Herrmann and Mouch prepare to take their officer exams. Cruz receives a chilling omen. Carver takes care of a dog after its owner is injured on a call.

Cruz's past comes back to haunt him. Severide prepares to teach an arson class at the academy. Mouch searches for a victim's next of kin.

The team responds to a crisis at a community center. Severide is forced to investigate one of his own squad members. Kidd helps a teacher going through a post-incident spin-out.

Chicago's first responders unite in the wake of a catastrophic gas explosion and fire that threaten a city government building. Herrmann reluctantly shadows Pascal while Violet, Novak and Dr. Frost take charge of triage efforts on site.

The crossover continues on Chicago Med S10E11 In the Trenches (II) and Chicago P.D. S12E11 In the Trenches (III).

Herrmann investigates the rise in missing fire hydrants and teams up with Kylie to track them down. Kidd's cousin comes to town, revealing surprising family history. Violet and Novak treat the victim of a birthday cake smash gone awry.

After a daring rescue at an adventure park, Kidd asks Severide to create a ropes course for Girls on Fire. Violet’s former nemesis returns, pleading for her help.

A surprise visitor from Novak's past joins Ambo for a late-night ride-along. Herrmann faces a mountain of Chief-level training records and incident reports. Violet catches Carver in a lie.

Kidd and Severide eagerly await big news. Pascal searches for the perfect anniversary gift.

In the face of adversity, Pascal searches for justice. Violet struggles to write a letter to Carver. Damon returns to the floater pool hoping to secure a permanent spot at 51.

Kidd connects with a troubled teen interested in Girls on Fire. Cruz, Capp and Tony wait to try out Squad’s new saw. Violet and Novak are stumped by a bodybuilder who passed out at the gym.

Deputy Commissioner Boden returns to Firehouse 51 to investigate a disastrous firefight and the surrounding mystery that left one of their own in peril.

Severide investigates an old house fire from 10 years back in which Kidd had responded. Carver and Violet search for a mystery medic who abandoned a victim. Novak looks for a roommate.

With the crew stretched thin, a performance efficiency expert evaluates Firehouse 51. Kidd and Severide bond with the mother of the baby they hope to adopt.

Kidd strengthens her bond with Natalie during a road trip. Severide investigates a car fire and uncovers surprising evidence. Violet receives a career opportunity after being featured in a local newspaper.

Severide puts his job on the line to help out one of their own. Kidd navigates Natalie’s complicated relationship with her sister. Herrmann prepares to take the Chief test.