The 126 crew responds to a military tank on the loose in downtown Austin and a human pile-up at the roller derby. Meanwhile, new paramedic captain, Tommy Vega, joins the team and Owen is reunited with his ex-wife and T.K.'s mother, Gwyneth, and receives an update on his cancer.

After a volcanic eruption wreaks havoc in Austin, the members of the 126 race to save lives at a college pool party, a family's mini-golf outing and a woman trapped in her food truck by a horde of scorpions.

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.

The 126 is on the scene when a disastrous wedding comes crumbling down, as Grace helps a dominatrix and her slave involved in a shocking situation. Meanwhile, Owen and Gwyneth struggle to label their new relationship and a man from Marjan's past re-enters back in her life.

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 who's 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.

Grace and Judd fight for their lives in the aftermath of the horrific car accident, as flashbacks show how a childhood tragedy led Judd to meet Grace and how they ultimately fell in love.

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.

After being forced to take time off work to recover from his surgery, Owen finds himself immersed in the search for a serial arsonist. Meanwhile, T.K. and Carlos take their relationship to the next level and Marjan copes with the aftermath of losing someone on the job.

A recovering Owen becomes the prime suspect in the serial arsonist case. Meanwhile, T.K. and Carlos find themselves in a fiery situation and Tommy gets the surprise of her life.

Owen helps Tommy through a personal emergency.

Owen and the members of the 126 race into action when a massive dust storm engulfs Austin. Season finale

Owen Strand, the lone survivor of his Manhattan firehouse on 9/11, takes his progressive philosophies of life and firefighting down to Austin, Texas, where he helps the firefighters of Firehouse 126 start anew.

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.

Judd calls out Owen's preferential treatment of T.K.. Marjan feels ostracized at her new mosque after another rescue video goes viral. Owen helps Michelle uncover new information about her sister's disappearance.

A massive tornado sweeps through Austin, as Owen, Michelle and their teams race to save those in its path.

The crew race to a brawl at a male strip club, a fire at a bull semen factory and a protest where male toxicity is taken to a new level; Grace tries to reconnect with Judd; Owen faces the consequences of his chemo.

Emergencies include a ride-share trip gone awry, a farming accident and a memorial service that may turn into another funeral. Owen unexpectedly bonds with the former Captain of the 126 (guest star Billy Burke), while Marjan and the crew help Mateo try to pass his written exams.

The crew deal with a runaway bull at a used car lot and an apparent electrocution at the hands of an LA transplant; Michelle gets the strongest lead yet on her missing sister.

The crew race to a rattlesnake infestation, and attempt to rescue a man with dementia from a dangerous scene he created; Michelle learns the truth behind her sister's disappearance; A tragic accident shakes the crew to its core.

Owen and the 126 crew race to a gender reveal party gone horribly wrong, and a father/son trapped in a cave during a spelunking excursion. Meanwhile, Owen helps T.K. reconcile the past to help his future, Judd and Grace aid Judd's aging father.

Owen helps T.K. reconcile the past to help his future; Michelle learns the full truth about Iris.