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.
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.
As the citywide blackout continues to cause mayhem in Los Angeles, Athena races to save her family from a tragedy. Meanwhile, Eddie must make a difficult choice about his future, and Maddie makes a life-changing decision.
The members of the 118 arrive on the scene after a truck crashes into a high school homecoming parade. Meanwhile, Athena and Michael try to help Harry in the aftermath of his kidnapping, May is intimidated by returning call center legend and Bobby gives a devastated Chimney advice regarding Maddie.
The members of the 118 face an awkward rescue call when they arrive on the scene of a man who has over-exerted himself exercising. The team also must save the life of a groundskeeper whose chainsaw cut into him and race to an explosion at a retirement community. Meanwhile, Athena has an extreme reaction to Harry's new behavior. Then, Hen and Eddie, as well as Buck and Ravi, have rocky starts to their new partnerships, and May receives an emergency call from a suicidal teen, while continuing her uneasy work relationship with Claudette.