A new face at Firehouse 51 causes tension, while rising chaos in the city brings new challenges to the team. Herrmann stalls on plans of relinquishing his office to Mouch.

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.

When an act of arson harms someone close to the Firehouse 51 family, Severide must track down the perpetrator. Impending budget cuts push Mouch and Pascal to get creative.

A member of the Firehouse 51 family remains in peril. Cruz lends a hand to Severide in the ongoing investigation.

Novak explores a new romantic connection. Vasquez deals with the aftermath of his father's recent release.

Herrmann grows uneasy when a local accident attorney inserts himself into a routine call. Firehouse 51 gets a visitor.

Pascal finds himself under intense scrutiny when a member of the firehouse is injured on a call. Herrmann grapples with family issues.

Firehouse 51 is called to an airfield when a passenger jet suddenly goes silent mid-air, triggering a high-stakes emergency. Their discovery cracks open a bigger and deadlier mystery - one with consequences that could put countless lives in jeopardy.

Severide is on high alert to track down a reckless driver who puts one of their own in harm's way. A member of Firehouse 51 struggles with a potentially life-changing decision.

A car crash puzzles Kidd and Vasquez. Herrmann gets his chance in the spotlight. Violet and Novak deal with a moral dilemma.

Severide overcomes new obstacles at the firehouse. Cruz finds himself at a loss amid family changes.

After a devastating fire erupts at a surgery center, Kidd works to hunt down the true cause. Violet, Novak and Vasquez grapple with shifting relationships. Molly's hosts its first trivia night.

While in the field, Violet and Novak are thrust into a dangerous and rapidly escalating situation, forcing them to rely on their instincts to protect both themselves and a vulnerable patient.

Severide investigates a fire at an abandoned store inhabited by squatters; Mouch pens a memoir about his life.