Vasquez fights to prove himself at 51; Violet and Novak pursue a troubling mystery; Herrmann is on a quest to keep Molly's profitable.
When city budget cuts stretch crews thin, Pascal takes matters into his own hands; Vasquez looks to an old friend for help; an incident in the field hits close to home for Violet.
Firehouse 51 must band together after a devastating fire catches them off guard; Vasquez continues his quest for answers; Violet and Novak face an unexpected roadblock in the new training protocol.
Cruz hunts for the identity of an unknown ally; Mouch takes steps to help a friend; Vasquez must make a difficult choice.
A traffic jam forces Violet and Novak to take drastic measures to save a patient; Severide shadows Pascal for a day; Kidd goes the extra mile for Isaiah.
Severide investigates a suspicious high school fire; Novak gets an unexpected call; Violet brings a 51 firefighter onboard the ambulance for a shift.
Casey struggles to get Boden to sign off on an energetic new recruit; Foster extends an olive branch to her irritating new medic; Otis inspires Herrmann to seek new partners at Molly's; Brett realizes life in Fowlerton will take some getting used to.
Brett and Foster question the suspicious circumstances surrounding an attack at a juvenile detention center; a convoluted new technology at Firehouse 51 tests everybody's patience; Kidd is chosen to represent the district at a leadership conference.
A rare but deadly bacteria takes its toll on numerous victims around the city, leaving Chicago's finest first responders to work together alongside the CDC to resolve the dangerous situation; Severide suspects something bigger is happening.
Kidd must prove herself at the National Firefighter Leadership Conference, while the rest of Firehouse 51 is called to two eerily similar car wrecks; Mouch tries to keep the firehouse informed by starting a newsletter; Cruz deals with a heartbreak.
Cruz and Severide suspect foul play when a fire started by an elderly woman turns deadly. Kidd, Foster and Brett create a women's-only lounge. Firehouse 51 celebrates some good news.
Severide must make a tough decision about the future of his career at Firehouse 51; Herrmann deals with the consequences of his temper; Cruz is excited to demonstrate the Slamigan at the Firefighting Expo; Commissioner Grissom returns.
Severide and Boden search to uncover whether arson was the cause of a fire at a hair salon; Mouch, Herrmann, Otis and Kidd make a startling discovery while tracking down the missing piercing nozzle from Engine 27.
Severide and Kidd continue to investigate Benny's old arson case; unexpected news leads Brett to ponder a big decision; all hell breaks loose.
Chief Boden makes a risky last minute decision to save his men; Dawson continues to deal with her father; Brett's childhood friend visits and strikes the attention of someone within the firehouse; a fire at a high school hits close to home for Boden.
Casey and Dawson run into a problem when they apply to permanently adopt Louie; Jeff Clarke gives an interesting proposition to Severide; Otis persuades Herrmann to throw a party at Molly's to celebrate the bar's 100th anniversary.
Dawson and Casey face legal issues as they try to retain legal guardianship of Louie; Severide continues to look for a bone marrow procedure to help Anna; Brett opens up to Dawson.
Severide agrees to a bone marrow donation; Casey and Dawson attempt to find harmony at home; Otis and Mouch plan to create a PSA to encourage people to join the Chicago Fire Department.
A dangerous man is on the loose with a vendetta against Lt. Casey and the Firehouse 51 squad; Antonio's ex-wife appears; Casey has a gift for Dawson.
Chief Anderson feels his authority was undercut after Chief Boden makes a decision that overrides Anderson's when both squads respond to the scene of a dangerous accident; Severide ponders a lifechanging decision; Herrmann does a good deed.
Citing a need for improvement, Chief Anderson reassigns members of 51 to other firehouses, leaving the crew members to make the best of their respective new situations; Severide struggles with an important decision.
Fire and rescue are called when an old warehouse-turned-work space turns into a firestorm, trapping countless victims; the doctors and nurses of Chicago Med deal with a barrage of patients as victims of the disaster are brought through the doors.
Members of the fire and rescue squads become hostages when a group of armed gang members invades and assumes control over Firehouse 51 during a turf war.
A series of similar car accidents raises suspicion that someone may be targeting innocent people; Severide tries to make Anna feel welcome in her new Chicago surroundings; a persistent constituent asks for Alderman Casey's help in resolving an issue.
Casey discovers a new crack house on the block that's harboring a female junkie; a new trainee gets Dawson and Brett into trouble; Severide gets an unexpected visit from his father.
Casey reunites with a former colleague; Dawson and Brett serve their time in retraining; Severide tries to fix what's going on with Anna.
Casey takes extreme measures to help his friend Kannell; Severide helps an old widow come to terms with letting go; Otis and Cruz find a new roommate.
Mouch offers to help when an off-duty incident puts Cruz in a bad spot; Casey takes on a powerful politician; Lt. Severide makes life difficult for a new team member; Dawson gets an unexpected visit from her father.
A warehouse blaze puts the fire and rescue squad at risk; Dawson's father overstays his welcome at Dawson and Casey's home; Casey fights for his first responders bill; Mouch makes a serious decision; Herrmann tries to make a young boy smile.