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.

In the aftermath of the dam break, massive mudslides wreak havoc throughout Los Angeles.

The 118 race to the rescues with emergencies at a spin class; in a hair salon and to a husband and wife in a compromising position; Buck discovers new cognitive abilities post lightning strike; Hen and Karen are concerned when they find out Denny has been seeing his biological father behind their backs; Maddie and Chimney enlist Athena and Bobby's help with a suspicious neighbor.