The 126 race into action when a horse barrels into a brewery with an unconscious rider on its back and then to a bus full of tourists all experiencing seizures. Judd introduces Owen to Wyatt's mother Marlene. Carlos and T.K. start couples counseling, when Carlos investigation into his father's murder becomes all-consuming.

The 126 are called on the scene to a hoarder's rat-infested house, then are trapped in an elevator as a woman goes into labor. Tommy and Trevor host his ex-wife Cassandra for dinner which goes awry.

The 126 race to contain a toxic chlorine cloud of death unleashed by the train derailment. Owen names the station's new lieutenant as Judd finds a path forward.

The 126 race into action when a major train derailment causes multiple injuries; Meanwhile Tommy makes a bold move in her relationship with Trevor; Wyatt asks Owen to give Judd his job back as Marjan and Paul continue to compete for the open position.

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. Owen attends group therapy with Tommy to deal with his brother Robert's death; 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.