No job is more stressful, dangerous or exhilarating than those of the Firefighters, Rescue Squad and Paramedics of Chicago Firehouse 51. These are the courageous men and women who forge headfirst into danger when everyone else is running the other way. But the enormous responsibilities of the job also take a personal toll. With big reputations and hefty egos, the pressure to perform and make split-second decisions is bound to put squad members at odds. When a tragedy claims one of their own, there's plenty of guilt and blame to go around. When it's "go-time" though, they put their differences aside and everything on the line for each other. From renowned Emmy-winning producer Dick Wolf.

Firehouse 51 is called to the scene of a harrowing and challenging disaster

When the team responds to a semi-truck leaking hydrochloric acid in a busy intersection, Casey (Jesse Spencer) and Dawson (Monica Raymund) find their relationship being put to the test. Meanwhile, Severide (Taylor Kinney) learns more about Brittany’s (guest star Serinda Swan) past and Mouch (Christian Stolte) has some difficulties in his dating life.

A house fire leads members of the truck and squad to race to save the lives of the couple trapped inside, and then are faced with the perplexing aftermath. Meanwhile, Chief Boden (Eamonn Walker) prepares to start his new family, while the combination of life at work and home pushes Casey (Jesse Spencer) and Dawson (Monica Raymund) apart. Elsewhere Molly’s II has its chance to shine at the Chicago Holiday Fest.

The firehouse receives unsettling news when two of their own come up missing following a routine call, prompting members of Chicago P.D. to lead the search. Meanwhile, Casey (Jesse Spencer) and Dawson (Monica Raymund) have a hard time figuring how to juggle their personal and professional lives. Elsewhere, Chief Boden (Eamonn Walker) and Donna struggle with news that their newborn has potential complications and they receive a surprise out-of-town visitor.

Casey (Jesse Spencer) comes to the aid of his sister Christie (guest star Nicole Forester) and faces down his corrupt brother-in-law, while Brett (Kara Kilmer) goes above and beyond for a mother in need. Elsewhere, Mills (Charlie Barnett) gets educated on the exciting world of unlicensed private investigation and Dawson (Monica Raymond) begins training with Herrmann (David Eigenberg).