A family of victims from a house fire are rushed to Gaffney. Lenox fights to save two sisters injured in an all-night rave turned tragedy. Tensions mount between Goodwin and Abrams over difficult staffing changes.

Things get personal when Ripley and Archer butt heads over the treatment plans tied to an unusual case, and a crisis at a nearby condominium brings an influx of patients. Meanwhile, Asher makes a surprising discovery with an expectant couple, a patient throws the hospital into chaos, and some familiar faces return to Gaffney.

Lenox and Frost receive an unusual request from the parents of a patient on life support. Ripley and Charles work with a man who can't remember who he is.

Charles races to convince a patient to accept treatment before it's too late. Frost bonds with a young girl battling immunodeficiency. Lenox makes a chilling discovery.

A personal clash between Asher and Archer reaches a breaking point. Charles and Ripley uncover a rare neurological disorder in a patient. Goodwin's personal life is put to the test.

Secrets are uncovered when Goodwin's family comes together for Bert. Ripley and Frost treat two children stung by hornets in a treehouse. A member of the team struggles with relationship woes.

Charles grows increasingly suspicious of a colleague's intentions. Lenox crosses a line to protect a patient. Hannah and Archer treat a soon-to-be father battling cancer.

The doctors deal with the professional and personal fallout from the choices made during a city-wide power outage.

Tensions spike when a road rage incident sends three patients into the ED. Frost's former television co-star resurfaces. An unexpected arrival catches Asher and Archer off guard.

Archer and Frost confront a troubling medical mystery while treating a college basketball player. Lenox's treatment of a surrogate patient leads to unexpected complications for the patient and her best friend.

Old resentment stirs up Charles when his best friends from med school visit. Hannah is forced to overcome obstacles in the treatment of one of her patients. Ripley looks to honor his best friend, Sully, on the one-year anniversary of his passing.

Charles faces a new challenge when three medical students shadow him for a day. Goodwin faces a high-stakes board meeting. Frost reckons with his past.

Firehouse 51 is called to an airfield when a passenger jet suddenly goes silent mid-air, triggering a high-stakes emergency. Their discovery cracks open a bigger and deadlier mystery - one with consequences that could ripple far beyond the runway and put countless lives in jeopardy.