When a powerful tornado tears through Nashville and endangers a country music festival, Capt.Don Hart leads fire station 113 on a harrowing rescue mission; the Hart family contends with the fallout when a long-held secret is revealed.
A tornado's path leads the Station 113 team to an intense rescue at a water tower; Ryan and his wife reach a turning point; Dixie has an assignment for Blue; Cammie coaches a distressed teenager through her mother's childbirth.
Amidst multiple crises, Ryan steps up to lead Station 113; the team responds to a dangerous call of a child trapped in a trailer hanging off a historic Nashville bridge; Blythe pays a long-overdue visit to Dixie.
Don and the 113 team respond to emergencies at a waterpark and a sorority house; the crew puts Blue's skills and knowledge to the test as he trains for his firefighter exam; Blythe digs into Blue's past.
With mounting pressure from his peers and family, Blue takes his firefighter exam; Roxie and Taylor search for the identity of an unconscious girl and respond to a high-stakes emergency involving two abducted children.
As Don, Blue and Ryan take extreme measures to prevent a distillery explosion, the 9-1-1 call center is disrupted by budget cuts and hackers; Blythe faces an emergency of her own.
Nashville is under siege, with each missed ransom escalating the stakes; as the city descends into chaos, Don grows desperate after losing contact with Blythe and races to find her before it's too late.
Time is running out as ransom demands and medical emergencies escalate; a power outage triggered by hackers wreaks havoc at the hospital.
Roxie notices Don is having panic attacks; Cammie begins to face reality when she starts attending a grief counseling group.