A fire claims the life of a team member in the premiere of this drama series following the firefighters, paramedics and rescue squad of Chicago Firehouse 51. Following the tragedy, Lt. Matthew Casey and Lt. Kelly Severide point fingers at one another. Casey also deals with personal dramas surrounding his separation from his wife, Hallie.
Severide is still consumed with guilt over Andy Darden's death and his remorse is only intensified when he learns that Darden's widow also blames him for the tragedy. Elsewhere, the team must rescue two teens trapped in a car; and Casey and Hallie try to hash out their next steps.
Casey faces pressure to cover for a cop's son who was responsible for a drunken-driving accident that left a teenager paralyzed. Meanwhile, Severide ignores his doctor's warnings that his neck injury may never heal if he doesn't seek treatment; and Mills must choose between working at the fire department full-time or helping his mom with her restaurant.
Chief Boden is plagued by bad press and low morale in the department after being accused of leaving a homeless man to die in a warehouse blaze. Meanwhile, Severide helps an elderly woman; Det. Voight continues to intimidate Casey; Shay runs into her ex-girlfriend during a call; and Hermann gets angry during a Halloween rescue.
Casey fights back against Det. Voight and ends up dealing with the consequences; Dawson's on-the-job behavior results in disciplinary action; Severide's arm fails him during a rescue, so he seeks the help of a pharmaceutical representative who happens to be his ex-lover.
Casey risks his life during an apartment-fire rescue, potentially earning a much-needed break from Det. Voight's ongoing pressure to retract his statement. Meanwhile, Dawson gets help from a girl she saved.
Severide delays taking a drug test after he and the rest of the firehouse staff are exposed to a meth lab over the Thanksgiving holiday. Elsewhere, Truck and Squad run into problems while coming to the aid of a gang-related shooting victim; a deep-fried-turkey fire gets out of control; Dawson rescues a bleeding man; and Casey delivers a baby in the midst of a traffic accident.
Peter begins to have doubts about his future as a firefighter after he comes across a young victim's body at the site of a train accident. Elsewhere, Dawson and Shay deal with an abusive mother; Severide saves a heart-attack victim, aggravating his own injury in the process; and Shay sends Clarice back to her husband.
Jose Vargas is injured in a fire and forced to go on disability leave; Chief Boden counsels a suspected teenage arsonist; Severide gets a tempting invitation from a woman he once rescued from a car crash; Cruz tries to save his younger brother from gang involvement.
Several of the firefighters are accused of stealing an expensive diamond necklace after responding to a kitchen blaze in an upscale townhouse. Meanwhile, Cruz tries to save his brother from involvement in an escalating gang war; Dawson invites Casey to a Christmas party; and Shay grows frustrated with Severide.
Cruz is overcome with guilt over Flaco's death and turns to Casey. Meanwhile, Shay recovers from head trauma; Severide asks Dawson to help him cope with his injury; Casey has family troubles; and Hermann has a hard time accepting a business deal.
Severide tells Chief Boden about his injury and makes some difficult choices about his future. Meanwhile, Casey has family issues; and Dawson goes on a rescue call and finds only one survivor—a young girl.
Chief Boden goes to the police after teenage arsonist Ernie starts a deadly hardware-store fire. Meanwhile, Severide reaches out to his father after making a decision about his future; Otis works a few shifts at a slow firehouse; and Dawson and Shay find themselves in trouble during a call to a tenement apartment.
Severide shares a past with a visiting lieutenant; Dawson tells Shay about her secret; Casey has family problems; Boden and his team deal with a bad batch of heroin; and Clarice and Shay are confronted with a new problem.
Dawson goes behind Antonio's back and puts herself in danger in an effort to help him with an investigation. Elsewhere, Casey and his mom struggle with their new relationship; Severide visits someone from his past as a favor to Lt. Whaley; and Herrmann and Otis learn the hard truth about their silent partner in the bar.
Cruz suffers from emotional distress, and ends up putting himself and his colleagues at risk. At the same time, Casey, his sister and their mom try to hash out their problems; Severide reaches out to someone from his past; and some members of the squad experience a change of perspective after responding to a dangerous call.
Severide's father clashes with Chief Boden over their former colleague's death; Mills helps an upset driver after a car accident; Shay makes a decision about her future with Clarice; and Hermann investigates a mystery with help from Otis and Dawson.
A rescue attempt at a tenement building ends in tragedy. Elsewhere, tensions run high when Severide decides to prepare Mills for a move from Truck to Squad; Shay and Dawson deal with a junkie's erratic behavior; and the team members have a run-in with local drug dealers.
Despite Severide's support, Mills faces resentment from his colleagues about his desire to join Squad. Meanwhile, a paramedic candidate works a few shifts with Dawson and Shay; Shay helps a pregnant woman who is suffering from complications while her husband is out of town; Dawson and Casey become closer; and Casey gets a surprise visit.
A former paramedic candidate accuses Severide of sexual misconduct. Elsewhere, Det. Voight returns to collect on a favor that Dawson owes him; Casey falls back into bad habits; and Dawson, Herrmann and Otis become bar owners.
Severide pushes back against the allegations leveled against him, antagonizing Chief Boden and gaining an unlikely ally in the process. Meanwhile, Casey finds personal happiness; Mills and Dawson face relationship challenges; and the squad responds to an apartment-building collapse.
Casey must team up with the Intelligence Unit, which is now headed by an unrepentant Voight. Meanwhile, Shay looks forward to parenthood; Mills and Dawson deal with personal issues; and the house comes together to support Molly's grand opening.
The first season concludes with the squad facing an unstable situation at the Cook County jail. Meanwhile, Shay is optimistic about starting a family; Hermann's wife goes into labor; and Mills and Dawson deal with major decisions.