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.

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.