A night at an amusement park takes a deadly turn when a roller coaster malfunction leaves lives hanging in the balance. Abby reaches out to Buck; Athena and Hen respond to an unusual home invasion.

The crew races to an emergency when disaster strikes at an Indian wedding. Abby enlists the help of Buck to try and find her mother and, for the first time, meets Athena face-to-face. Meanwhile, Bobby has a difficult time confronting his past and Hen struggles to make the right decision.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator and extreme hoarders entombed in their house. Meanwhile, Athena jumps into to the dating pool, as Buck and Abby's relationship is tested by her ailing mother.

On one of the hottest days of the year, the first responders feel the pressure as harrowing incidents keep happening around the city, including a road rage accident involving a van full of tourists, an emergency at an auto-repair shop and a grenade. Meanwhile, Buck gets a surprise visit from his sister, and a handsome new hire Eddie jeopardizes Buck's chances of being chosen for a fireman calendar.

When the first responders race to the rescue of a crashed news copter, they unwittingly become the subject of an eager reporter's first on-air assignment. Meanwhile, Bobby tries to deal with his daughter's death, as Athena prepares for May's homecoming dance. Then, Maddie struggles to let go of her fear of the past. Also, the team responds to emergencies at an eating contest, a bodybuilding competition and a toddler pageant.