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

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 118 responds to debris from a meteor shower crashing into an apartment building and a deadly fire caused by a hazardous waste truck crash inside a tunnel. Meanwhile, Hen struggles with guilt over her ambulance accident, Bobby introduces Eddie to an old friend to help with his anger and Maddie receives an urgent call for help.

Accidents happen at a bowling alley and a home renovation; Athena pursues a car thief.

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

The 118 races to rescue a little girl in a runaway hot air balloon and help with a city power outage caused by a hijacked tree-trimmer truck; Athena's investigation into a serial rapist case puts her life in jeopardy.

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.

The members of the 118 rush to the site of a hit-and-run that leaves a familiar face in critical condition. Meanwhile, with Buck's help, Athena investigates the case of a missing woman last seen in a casino and Josh recalls an emergency in 2006 that led him to become a 9-1-1 operator.

When a famous mystery writer dies, Athena, Bobby and the 118 respond to the chaos caused by a city-wide manhunt for buried treasure the author left behind.

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.

A man over-exerts himself exercising; a groundskeeper is cut by his chainsaw. An explosion occurs at a retirement community. May gets an emergency call from a suicidal teen.

Bobby and the 118 race to save lives after an explosion rocks the hospital where Dr. David Hale is performing surgery. Meanwhile, Michael makes a life changing decision.

Athena, Bobby and the 118 "speed" to the rescue to save a family whose pick-up truck has been rigged with a pipe bomb which will detonate if the vehicle slows under 55 miles an hour. Meanwhile, Eddie has a rough transition into his new job, Buck makes an impulsive relationship decision and Hen is reluctant to accept her new partner in Chimney's absence.

Another day in the life of the 118, as its members race to rescue a cliffside wellness retreat guru after his followers turn on him. Then, they respond to an emergency call at an upscale hair salon. Meanwhile, Maddie contemplates returning to work, Eddie and May make decisions on their future, as do Buck and Taylor, and the 118 gathers for a surprise wedding.