Athena investigates a mysterious murder during a neighborhood block party and the 118 rush to save lives endangered by a bomb threat. Meanwhile, Chimney has a hard time keeping secrets when Maddie and Buck's parents come to town.

The 118 race to save the lives of workers trapped in a five-alarm factory fire. Meanwhile, Maddie reveals a painful family secret that causes Buck to confront his childhood and answer why he is the daredevil he 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.

As Buck's life hangs in the balance, he dreams of a world where he never became a firefighter, for better and worse.

Hen and Karen welcome a new addition to their family, while a call unfolds involving a person’s limb that’s taken on a mind of its own. Meanwhile, Eddie and Marisol take a closer look at their relationship, and Buck navigates his new feelings.

After years of anticipation, Maddie and Chimney's long-awaited wedding day arrives. However, when the groom mysteriously vanishes, the 118 races against time to ensure he doesn't miss the most crucial day of his life.