Buck jumps back into the dating scene but fears he will return to his old ways; a woman goes to great extremes on a freeway overpass to get the attention of her husband; a couple have a car accident on their wedding day.

When Metro LA's 9-1-1 system is hit with a massive system-wide power outage, the call center must go old school in responding to emergencies. The first responders must deal with explosions in multiple homes and a difficult child birth. Meanwhile, Michael confronts Bobby about parenting his kids.

The 118 deals with a situation where a stunt driver is placed in a precarious position, two mail bombs are detonated and a teenaged social influencer loses their mind; Eddie's family decides to visit; Buck confronts a deadly series of events.

In the aftermath of the shooting, Athena and the 118 are on high alert when a sniper is targeting members of the LAFD. Meanwhile, Maddie makes a life decision. Season finale

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.

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.

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.