While running a secret errand, Dawson finds herself trapped in a collapsed parking structure. With all paths of exit blocked, she is forced to improvise and works double-duty to keep a number of injured individuals alive while trying to maintain peace among those trapped. Meanwhile, pressure is mounting on Casey as he begins to take on additional duties, Kidd grows increasingly skeptical of Hope after learning about rumors circulating and the firehouse receives a surprise visitor.

Boden has a lapse in judgment in the aftermath of rescuing a young boy. Kidd struggles to win the approval of Severide's mom after a surprise visit and Otis takes on new responsibilities at the firehouse.

Members of Firehouse 51 are dismayed to learn their boundaries have been redrawn to overlap with an adjacent station and problems quickly arise. Casey and Gallo hunt a missing piece of equipment. Brett and Foster find themselves at odds. Mouch tries the find the recipient of a mysterious letter he discovers.

Boden is on edge after starting a new fad diet. Casey and Severide disagree on a call. Brett’s birth mother shares life-altering news. A familiar face has a proposition for Herrmann.

While completing a task assigned by headquarters, Boden makes an unforeseen connection. Gallo is forced to make a surprise rescue to one of their own when the firehouse is called to the site of a construction explosion. Mouch reignites an old feud.

Gallo makes a split-second decision during a dangerous fire rescue leaving Casey steaming that his direct orders were not obeyed. Kidd feels a strain in her relationship with Severide. Brett and Mackey find themselves searching for answers following a series of suspicious calls.

A call to a familiar location brings back mixed emotions for Severide. Herrmann heads out for a vacation. Casey is not thrilled with his replacement.

A video of Casey from the roof rescue goes viral. Mouch sets up a Little Free Library at Firehouse 51. Herrmann breaks protocol.

A major security breach in the city’s computer networks forces Firehouse 51’s senior leaders to take matters into their own hands. Severide gears up for an arson investigation.

Stella Kidd returns to Firehouse 51. The team must work together to put out a potassium fire in a tunnel. After that incident, Ritter begins to worry about a young cop who witnessed the fiery death of a truck driver.

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.

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 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.

After their defibrillator malfunctions on a call, Brett and Violet search for answers. Herrmann tries to find the perfect home for his new recliner. A secret from Gibson's past comes to light.

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.

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.