A massive tsunami hits the Santa Monica Pier, placing Buck and Christopher's lives in danger .

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

Athena, Maddie, Bobby and the 118 races to save lives after a massive tsunami hits the Santa Monica Pier and Buck fears the worst when Christopher goes missing.

The First Responders rally together to search for a missing Maddie.

The 118 races to the rescue when the 9-1-1 Call Center goes up in flames. Then, Bobby risks his life to save a trapped May, and Claudette, Buck and Eddie work together to help an injured electrician, and Chimney and his brother team up as firefighters for the first time.

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.

Maddie fears for herself and her co-workers when the call center is taken hostage.

The 118 responds to a fire at a local animal shelter and races to evacuate all the animals. Meanwhile, Maddie takes a 9-1-1 call that sets her on a quest for answers.

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.

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

A series of ransomware threats leads to an overabundance of emergencies for the 118, including a medevac helicopter crash at a hospital and an air-traffic control tower system failure. Meanwhile Athena must revisit her traumatic attack when the case of the realtor serial rapist goes to trial, Eddie suffers a health scare and Maddie's postpartum depression worsens.

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.

Look back at how Chimney joined Station 118 and became the firefighter and paramedic he is today.

When a murder weapon from a case close to Athena in the early '90s resurfaces, flashbacks to 1989 show how Athena joined the LAPD and became the police officer she is today.

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's only chance of surviving and saving everyone on the flight is to attempt to land the plane before it crashes and call on the 118 for help.

The holidays are naughty and nice for the first responders, who must deal with a stampede at a toy store, a mistletoe stunt gone awry and neighbors competing in a Christmas-light showdown. Meanwhile, Bobby contemplates his future with Athena, Chimney and Buck attempt to lift Maddie's spirits and Eddie must decide if he wants to give his son what he really wants for Christmas - a visit with his mom.

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.

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.

Athena and the 118 race to save lives after a drunk driver causes a deadly pile-up on the freeway. Meanwhile, Maddie goes into labor and Hen and Karen are devastated as they prepare their foster daughter, Nia, to be reunited with her birth mother.

In the aftermath of a deadly plane crash, Bobby and team race to help the survivors, while Athena deals with panic and chaos at the airport. Bobby confronts his past demons; Athena is out for revenge against a group of teen bullies; and Abby delivers an important message from a 9-1-1 caller.

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.

Chimney is determined to find a missing Maddie amongst the chaos of St. Patrick's Day.

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.

Athena is tasked with safely delivering a prisoner to testify on a high-profile case. Meanwhile, a light plane is hit by a swarm of bees and sent careening into a passenger plane.