Casey makes a life-altering decision; Gallo, Ritter and Violet agree to an interview and photo shoot; Brett and Mouch launch the paramedicine program; Cruz comes closer to fatherhood.
Gallo, Violet and Ritter debut their microbrewery business at Winterfest; Brett prepares to present her paramedicine programme to an oversight panel; Firehouse 51 gets in the holiday spirit.
One of Erin's informants leaves witness protection to give an alibi for a former boss facing murder charges. Frank gets into a battle with the New York City Fire Department commissioner.
The return of The Freelancer unveils a conspiracy involving a local photographer; Ressler hits a personal milestone.