Despite the case being closed, Bobby is determined to prove his AA sponsor was murdered and bring his killer to justice; Meanwhile Buck struggles with his post-traumatic stress.

As Buck's life hangs in the balance, he dreams of a world where he never became a firefighter, for better and worse.

While in Florida caring for her ailing father, Athena and Bobby investigate the disappearance of her childhood friend from 45 years ago.

A dry thunderstorm rolls over LA, bringing in a series of lightning strike emergencies for the 118 and leaves a first responder's life hanging in the balance. Athena and May go undercover at the rehab facility to help Bobby with his investigation into his sponsor's mysterious death. Maddie dreads her parents visit to her and Chimney's new and unfinished house, while Chimney get a surprise of his own from a visiting Albert.

The 118 race to the rescue when a structure collapse at a "happiness convention" traps people under rubble. While on FaceTime with her mom, Athena's father suffers a stroke and crashes through the wall of his house. Hen stretches herself too thin with test prep and her new responsibilities at the 118, while Maddie tries to help new recruit get his bearings at the call center.

Hen fears for Karen's life when an explosion rocks her science lab on the day she brings Denny to work with her.

The 118 race to the rescues with emergencies at a spin class; in a hair salon and to a husband and wife in a compromising position; Buck discovers new cognitive abilities post lightning strike; Hen and Karen are concerned when they find out Denny has been seeing his biological father behind their backs; Maddie and Chimney enlist Athena and Bobby's help with a suspicious neighbor.

When a blimp suffers mechanical failure and its engine catches fire, Athena and the 118 must rescue victims both inside and outside a packed sports stadium. Bobby and Athena drop off May on her first day of college and discuss honeymoon plans, while Maddie and Chimney go to couple's therapy.

The 118 race to the rescue when a birdwatcher is trapped under a tree. Chimney is in for a wild ride when he tends to a drunk driver; Maddie helps a mother and her young daughter when an abusive father shows up at the their house; Eddie catches Christopher in a lie; Buck begins a year of "yes to possibilities" and immediately receives an interesting proposal from a former roommate.

The Santa Ana winds bring in a variety of weirder-than-usual emergencies as the 118 respond to a family dog retrieving a severed hand and a young woman sleep-driving into the station. Bobby worries about his AA sponsor. Denny questions Hen and Karen about his biological parents. Chimney thinks he's found the perfect house for him and Maddie.

The 118 race to the rescue at emergencies at a commercial bakery and a bodybuilding competition; Bobby's annual performance reviews sends Chimney to the firefighter academy where he runs into a familiar face; Eddie's aunt gets involved in his personal life; Maddie helps a nervous teen suffering a panic attack.

Athena and the 118 race to rescue when a wedding proposal tragically intersects with a bank robbery, and then when a princess bride is literally stuck on her way to the altar. Athena talks a victim thru her grief; Maddie takes matters into her own hands as Buck finds a surprise visitor on his doorstep.

Athena and the 118 race to the rescue when a fading movie star is plagued by a series of near-death experiences.

A series of freeway car accidents leads to a catastrophic overpass collapse that endangers the lives of civilians and members of the 118.

Athena investigates when the same house is hit with two home invasion 9-1-1 calls within hours of each other. The 118 race to the rescue when a D-I-Y home renovation traps a man in an attic. Hen asks for a second chance with her medical school professor. Maddie and Chimney regret hiring a nanny for Jee-Yun after the woman completely takes over their apartment.

The 118 race to the rescue at emergencies when a fire breaks out in an accountant's office and a car crashes into a "living funeral." Athena is shocked when a suspect dies in her custody minutes after she arrests him; Buck is attracted to a death doula; Maddie and Chimney panic when they are audited by the IRS.

The 118 race to the rescue at a renaissance faire, then an office building when an overbearing boss is poisoned. Athena fears for May's life when she encounters a disturbed young man. Buck babysits Jee-Yun as Maddie and Chimney begin house-hunting. Eddie and Carla prepare Christopher for his first school dance.

The 118 race to rescue two roommates desperately trying to find a needle in a haystack at a landfill, and help a woman whose nightmare dream suddenly becomes a painful reality. Athena and Maddie team-up to find a missing boy in a crowded mall; Chimney debates if the time is right to propose to Maddie.