It takes a team of people to help answer the famous question, "911, what's your emergency?" Detective Athena Grant works as a member of the police force, handling cases that require her sharp mind and expertise, while also trying to juggle her own family drama. Bobby Nash and his team of firefighters help execute the daring rescues that often come along with these life-threatening situations. Meanwhile, Abby Clark spends her days taking and fielding emergency calls at the 911 call center, but constantly desires to know what happens after she sends help.

A night at an amusement park takes a deadly turn when a roller coaster malfunction leaves lives hanging in the balance. Abby reaches out to Buck; Athena and Hen respond to an unusual home invasion.

The first responders take calls to help an unusual domestic disturbance, a "death" at a psychic's and a horrific motorcycle crash. Meanwhile, Bobby dips his toe into the dating pool, Abby takes a walk down memory lane, Buck is confronted by his past actions and Athena tries to start her new life.

On one of the hottest days of the year, the first responders feel the pressure as harrowing incidents keep happening around the city, including a road rage accident involving a van full of tourists, an emergency at an auto-repair shop and a grenade. Meanwhile, Buck gets a surprise visit from his sister, and a handsome new hire Eddie jeopardizes Buck's chances of being chosen for a fireman calendar.

The 118 springs into action when a city-wide blackout and a record heatwave causes mayhem in Los Angeles. Meanwhile, Chimney confides in Hen about Maddie's condition, and Athena's worst nightmare comes true.