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 and Dawson have a hard time figuring how to juggle their personal and professional lives. Elsewhere, Chief Boden and Donna struggle with news that their newborn has potential complications and they receive a surprise out-of-town visitor
Severide and Dawson discover startling evidence found at a storage unit fire that appears connected to the fire that took Shay's life. Meanwhile, the firehouse bands together when Chaplain Orlovsky is the victim of a bad car accident.
An ice storm hits, forcing a citywide lockdown. Mills and Brett are left stranded in the elements while searching for a teen, and the firehouse members babysit a newborn. Elsewhere, Severide receives a job offer, and Chief Boden clashes with his father over his treatment.
Interim Chief Pat Pridgen (guest star Matthew Del Negro) is brought over to temporarily fill in for Boden (Eamonn Walker), who is left to tend to his personal affairs. When tension is sparked as the result of his derisive leadership, the absence of Chief Boden (Eamonn Walker) becomes all too apparent. Meanwhile, Lieutenant Severide (Taylor Kinney) must deal with a most unwelcome addition to his squad, Brett (Kara Killmer) gets closer to a girl she previously rescued and Casey (Jesse Spencer) starts seeing a new woman, Beth (guest star Bree Williamson), but interesting...
Severide's old friend arrives, hoping for a second chance with the Chicago Fire Department. Meanwhile, Mills tries to regain his active squad status, Mouch confronts his fear about meeting his child, and Brett and Dawson set out to have a big night out.
Mills tries to save a driver who's been seriously injured in a car accident. Meanwhile, Casey has doubts about the owner of a remodeled strip club and Hermann, Otis and Cruz prepare for the peewee hockey championship.
An apartment fire connected to a case of rape and attempted murder resembles an unsolved case in New York, so Sgt. Benson of Special Victims Unit comes to Chicago to help Intelligence with the investigation.
At Sgt. Voight's urging, a determined Lt. Casey agrees to go undercover in an effort to provide proof of Jack Nesbitt shady dealings. Meanwhile, Otis and Severide continue to disagree about the integrity of Scott Rice, causing tensions to flare between members of truck and squad. Meanwhile, Herrmann helps out a fellow member of the firehouse.
Casey puts his life on the line and digs deeper into the shady dealings of Jack Nesbitt. With members of truck and squad at odds over Rice actions in the field, Chief Boden is left to figure out how to create unity in a divided house, while Severide comes to question his own judgment. A dangerous warehouse blaze quickly gets out of control and threatens members of firehouse 51, prompting Boden and Cruz to risk everything to save their own. Elsewhere, Dawson gets some life-changing news.