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 veteran with a live grenade embedded in his leg. Meanwhile, Buck gets a surprise visit from his sister, Maddie. Also, Athena questions her relationship with Bobby. Then, at the fire station, handsome new hire Eddie jeopardizes Buck's chances of being chosen for a fireman calendar.
When a massive earthquake rocks Los Angeles, the first responders rush to rescue victims from a crumbling high-rise hotel both under the rubble and high above the ground. Athena must deal with wreckage from a collapsed freeway overpass and Maddie is thrown into the fire as she faces her first crisis as a 911 dispatcher.
The first responders continue to deal with the fallout of a massive earthquake and its deadly aftershocks. Athena tries to keep the peace as Bobby and team continue to rescue victims from a collapsing high-rise hotel, both under the rubble and high above the ground. Maddie 's first day on the job involves helping a pregnant couple deliver their baby safely.
The first responders are dealt with a security guard stuck in between two buildings for several hours. A man gets trapped in a mall escalator. Meanwhile, Athena contemplates a lieutenant promotion, Eddie turns to Buck for help when it comes to his son with cerebral palsy. Also, Chimney goes for a check up following his accident and Maddie reveals to Buck that she decided to move out.
Wanting to see the faces behind the 9-1-1 calls, Maddie goes on a ride-along with Athena, while dealing with a seemingly “perfect” dispatcher back at the call center. Meanwhile, Hen must figure out how to save her family from permanently falling apart, and the first responders deal with emergencies both at a military funeral and a movie theater.
When the first responders race to the rescue of a crashed news copter, they unwittingly become the subject of an eager reporter's first on-air assignment. Meanwhile, Bobby tries to deal with his daughter's death, as Athena prepares for May's homecoming dance. Then, Maddie struggles to let go of her fear of the past. Also, the team responds to emergencies at an eating contest, a bodybuilding competition and a toddler pageant.
Halloween finds the first responders racing to the rescue at a cemetery, a haunted hayride and a spooky Hollywood parade; Meanwhile Maddie thinks she has received a “ghost” call from a missing hiker; Hen finds herself facing with a life or death situation with the father who abandoned her; Eddie reconnects with his estranged wife.
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.
Hen relives her evolution into the firefighter she is today as she recalls the first times she met Chimney and Athena.
The first responders face personal and professional challenges.
Bobby meets Athena's parents for the first time and Maddie attempts to end her marriage for good, causing Doug to insinuate himself even deeper into Chimney's life. Meanwhile, a tanker carrying a tiger shark crashes on the freeway and a gas leak in a plastic surgeon's office happens mid-surgery.
Look back at how Chimney joined Station 118 and became the firefighter and paramedic he is today.
The First Responders rally together to search for a missing Maddie.
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.
A going-away party for a bank manager turns into an emergency, and then a mystery, as the first responders are accused of pulling off a daring heist.
The first responders deal with a calamity at a chocolate factory; a mail bomb explosion; Eddie receives some surprising news from Shannon; Maddie contemplates her future in the call center.
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.