Watch Chicago Fire Season 4, Episode 1 Let It Burn Online

Lt. Casey, who is at the center of an undercover operation to bring down a trafficking ring run out of Nesbitt's strip club, finds himself in very dangerous territory. Meanwhile, as a result of the high turnover rate on squad, Severide gets a rude awakening when Capt. Dallas Patterson is brought in, much to Boden's dismay. Dawson confirms her suspicions that her life is about to change forever and Jimmy Borrelli, the new candidate, makes an unusual first impression. Elsewhere, citizens of Chicago band together to take charge of their neighborhood in protest of a drug den in their area, resulting in ramifications that severely hinder members of Firehouse 51, who are called to the scene to battle a blazing fire. From renowned, Emmy Award-winning executive producer Dick Wolf ("Law & Order" brand) and creators Derek Haas and Michael Brandt, the writing team behind "3:10 to Yuma", comes the high-octane drama "Chicago Fire", - an edge-of-your-seat view into the lives of everyday heroes committed to one of America's noblest professions. For the firefighters, rescue squad and paramedics of Chicago Firehouse 51, no occupation is more stressful or dangerous, yet so rewarding and exhilarating. These courageous men and women are among the elite who forge headfirst into danger when everyone else is running the other way and whose actions make the difference between life and death. The pressure to perform on such a high level has a way of taking a personal toll, sometimes putting team members from the Truck and the specially trained Rescue Squad at odds with each other. Despite any differences, this is an extended family, and when it's "go time", everyone inside Firehouse 51 knows no other way than to lay it all on the line for each other. When a tragedy claims one of their own, there's plenty of guilt and blame to go around. Lt. Matthew Casey (Jesse Spencer, "House"), in charge of the Truck, tries to carry on, but butts heads with the brash Lt. Kelly Severide (Taylor Kinney, "The Vampire Diaries") of the Rescue Squad - and each blames the other for their fallen team member. Adding to the turmoil, Casey, unbeknownst to his colleagues, is in the midst of a separation from Hallie (Teri Reeves, "Three Rivers").