Danny crosses paths with a criminal from a previous case when he investigates a gang attack with a shocking motive; Frank and Mayor Chase butt heads over an off-duty cop…

Frank must decide between remaining police commissioner and pursuing a new professional chapter when his old friend presents him with an exciting job offer. Danny and Baez investigate the murder…

In the aftermath of a chaotic event at a favorite Harlem hangout, Luke heeds the call to action — and hits Cottonmouth where he’ll feel it most.

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…