Owen Strand, the lone survivor of his Manhattan firehouse on 9/11, takes his troubled firefighter son, TK, and progressive philosophies of life and firefighting down to Austin, Texas, to help the firefighters of Firehouse 126 start anew. But as he assembles his new team of diverse and qualified candidates, Owen struggles with a secret he hides from the world - one that could very well end his life.
The crew races to a disaster at a wave pool, and an outbreak of mercury poisoning that is leaving its victims in a a zombie-like state. Meanwhile, Owen must come to terms with his illness and what the side-effects of treatment may do to his vanity. Also, Michelle follows a new lead on her missing sister while TK is unsure how to handle his budding relationship with Carlos.
Emergencies include an accident at a grain silo and a steak eating contest, plus an unusual home intruder. Meanwhile, Judd calls out Owen's' preferential treatment of TK. Also, Marjan feels ostracized at her new mosque after another rescue video goes viral. Then, Owen helps Michelle uncover new information about her sister's disappearance.
Owen, Michelle and the 126 crew race to a rattlesnake infestation at a young family's home, and attempt to rescue a man with dementia from a dangerous scene that he created. Meanwhile, Owen adopts a firehouse dog with cancer and Michelle finally learns the truth behind her sister's disappearance. Also, a tragic accident shakes the team to its core.
Chaos ensues in Austin when a solar storm causes the electricity and power equipment to malfunction. The 126 team has to rescue the passengers of a light aircraft caught in the lines of high voltage electric towers while transporting a sick man for a liver transplant. During an outing with Carlos, TK questions his relationship with him after Carlos begins asking. When the malfunctioning traffic lights cause several accidents, they rush to help people before the 126 arrives
As a wildfire spreads across Texas, Evan "Buck" Buckley, Henrietta "Hen" Wilson and Eddie Diaz from the 118 firehouse in Los Angeles arrive in Austin to help Capt. Strand and the 126. As the crews race to save a group of teenagers trapped by the fire at a campground, Owen and Hen fight for their lives in the aftermath of a helicopter crash.
Judd is shocked at the latest victim of an emergency call, Grace and Carlos must save a woman literally trapped in a domestic abuse situation and the 126 arrive at a horrific highway crash that threatens the lives of a father and daughter. Meanwhile, Owen and Gwyneth face a difficult decision in their relationship and Mateo regrets his new tattoo.
Owen and T.K. risk their lives to save two brothers trapped in a homemade minefield. Meanwhile, Grace receives an emergency call from a conjoined twin whose brother is dying, Tommy interviews new candidates to fill the team's open EMT position and Paul's mother and estranged sister pay him an unexpected visit.
The 126 arrive at a funeral where another dead body has crashed the burial, and then to a hospital where an MRI has gone haywire. Owen and Tommy each feel displaced in their homes as Gwyn moves into the Strand household and Charles seemingly becomes the full-time parent in the Vegas'. Meanwhile, T.K. makes waves in his new position.
A bank robbery, an apartment fire and a pregnant woman lost in a parking garage are the seemingly unconnected calls to which the 126 responds. Then, T.K. celebrates his one-year anniversary of sobriety, while Owen and Gwyn may not make it to the end of the week as a couple. Also, Carlos finds himself working on a case with his Texas Ranger father.
The 126 make calls to a bloody disaster at an ice cream shop and help rescue a boy missing from his own birthday party. Meanwhile, the 126 holds an "intervention" for Owen after he accidentally spills his secrets to new roommate Mateo. Then, T.K. and Carlos take a big step in their relationship, as Grace learns to rely on others in the aftermath of the car accident.
As the unexpected arctic cold front and ice storm continues to havoc in Austin, Tommy, T.K. and Gillian races to rescue a young boy who has fallen in a frozen pond. Judd and Mateo work furiously to help a trapped Paul and Owen takes drastic measures to save a man who has been stabbed and left for dead in the snowy hill country.
In an attempt to bond with Wyatt, Owen and Judd take the teen alien hunting, but their search takes a different turn when they find two dead bodies. Meanwhile, Tommy joins a grief group for widowers, as mysterious events around her house lead her to believe Charles is communicating from the beyond with her and the twins. Then, a woman fears she is cursed and takes drastic measures to cure herself.
When a dust-up between Owen and an obnoxious police sergeant goes viral, the existing tensions between police and fire rescue mount, leading Owen to decide they will settle the score on the softball field. Meanwhile, Grace competes against a hot shot call center night-shift operator when he moves over to the day shift.
Owen, Tommy & the 126 race to the rescue when a medieval-themed restaurant suffers a case of carbon monoxide poisoning. Meanwhile the crew is worried that Paul still has not mentally recovered from his surgery and his friendship with Marjan is over. Mateo is offered a promotion by his old fire captain, but quickly realizes he is not the man he once knew.
Owen and the 126 race to emergencies at a fast food drive-thru, a high school wrestling match and a case of road rage – all with one common element tying them together. Tommy’s estranged brother-in-law makes a surprise appearance in Austin. Marjan confronts Capt. Strand about his anger management issues.
Facing his anger management issues, Owen has a breakthrough in therapy. Then, after a particularly devastating emergency call, Grace reaches out to a co-worker, but regrets when Judd offers more than she was planning. Also, a clown has an emergency at a young boy’s birthday party and Tommy, T.K. and Nancy race to help a survivalist who has a painful encounter with a reptile.
Captains Strand and Vega along with the members of the 126 are called into action to a county fair when a "Derecho," a series of fast-moving severe thunderstorms, hit Austin, causing hurricanic and tornadic-force winds, heavy rains, flash floods and a wide path of destruction. Owen's newfound passion for motorcycling puts him on a potentially dangerous path. Tommy has the potential for a romance when she meets an attractive single father. And as T.K. and Carlos prepare for their wedding, a secret from Carlos' past may stand in their way to happiness.
As Owen gets pulled deeper into the FBI’s investigation of the motorcycle gang, Sgt. O’Brien makes a confession to him. Meanwhile, Grace and the 126 respond to a call from a man who claims his girlfriend slipped over the side of a cliff and Carlos searches for a missing friend, putting his own life in danger.
The 126 help a husband whose wife "dies" when she is not upside down. Grace takes a call from a pizza delivery driver who is in for the shock of his life. Tommy is worried Trevor's young daughter is a bad seed as she attempts to break them up. Paul is hesitant to go on a date with Asha, who knows him prior to his transition.
When she discovers her former fiancé is having a baby with his new wife, The 126 help Marjan enter the dating world through a series of chaperoned dates; Owen and the team are called to the rescue when a pregnant woman takes matters (and her anger) out at a motel where she suspects her husband is cheating on her.
TK & Carlos receive pep talks before their wedding.
Carlos and TK cut their wedding cake.
TK reveals what his last name will be.
The 126 race into action when an armored truck and its guards are attacked by a group of masked men. Carlos, in his new job as a Texas Ranger, is assigned to investigate the case. Both Marjan and Paul each apply for the open lieutenant position, replacing Judd, who finds himself lost without his old job. Wyatt begins work at the call center and a major train derailment signals tragedy.
The 126 race to save a man crushed under a vending machine. While struggling to handle his aggressive foster horse, Owen finally faces the truth of his brother's death. As Mateo and Nancy scramble to delete a nude photo of her accidentally sent to the 126, Tommy is concerned that Nancy may be facing a possible health scare.
TK gets a huge surprise on his 30th birthday when his stepdad Enzo arrives in Austin along with TK's young half-brother Jonah. Owen's resentment of Enzo turns physical. Tommy is determined to push through her latest crisis. Wyatt attempts to talk-down a suicidal caller and the 126 must perform a dangerous surgery in the field after a man is impaled in a tree.