When Metro LA's 9-1-1 system is hit with a massive system-wide power outage, the call centre must go old-school in responding to emergencies.

Mayhem unfolds at a going-away party for a bank manager as the first responders are accused of pulling off a daring heist.

A heartbroken Bobby Nash packs up and heads to Los Angeles for a fresh start, where he becomes captain of the 118 and meets Athena Grant.

The first responders deal with a calamity at a chocolate factory and a mail bomb explosion. Elsewhere, Eddie receives some surprising news from Shannon, while Maddie contemplates her future in the call centre.

A stunt driver is caught in a hairy situation, and a teenage social influencer is bugging out. Elsewhere, the city is on high alert after two mail bombs go off, Eddie's family comes to town, and Buck faces a life-or-death situation.

Athena enlists the 118's help when a teenager speeds out of control on the freeway. Meanwhile, a routine traffic stop uncovers a shocking kidnapping and Buck struggles with his recovery.

A massive tsunami hits the Santa Monica Pier in Los Angeles and places Buck and Christopher's lives in danger. The first responders must do everything they can in order to save as many lives as possible.

Athena, Maddie, Bobby and the 118 race to save as many lives as possible after a massive tsunami hits the Santa Monica Pier in Los Angeles, and Buck fears the worst when Christopher goes missing.

The first responders race to save workers in a high-rise during a fire drill, a mother and her sons are involved in a perilous car accident, and squabbling siblings fighting over a family heirloom.

The 118 races to help protesters at a slaughter house, and a wife finds herself trapped in a "rage room" with her husband's mistress. Athena takes action after Michael, and May and Harry experience a traumatic traffic stop.

Athena and the 118 respond to bizarre emergency calls on Halloween, including a flock of crows terrorising a field trip, an office employee having a close encounter with an eight-limbed creature and a ghost-like girl wandering a neighbourhood.