T.C. and Topher return to find Jordan in critical condition and San Antonio terrorized by snipers; Drew and Gwen get caught in the crossfire when a SWAT team corners the snipers.

Drew and Paul head to the scene of a multi-car collision while the newly-anointed Dr. Ragosa along with Jordan, Scott, Krista and Kenny, manage the deluge of incoming victims. Meanwhile, TC and Topher head into a war zone to treat an old friend.

A boy is suffering with a serious fever and his high-strung mother begins to show signs of distress.

A serious car crash results in two teens and a young pregnant woman arriving at the hospital, pushing the night shift members to their limit. Meanwhile, Paul tends to a quirky, wealthy hospital benefactor.

Drew takes action when a gunman attacks at a friend's promotion ceremony.

Topher takes over as chief of the night shift. TC is temporarily suspended. Jordan is scrutinized for her mishandling of the man who shot a recovered Topher. A father is trapped under an elevator. Ragosa returns to the ER.

The night shift is tested when a rancher accidentally shoots his wife. TC heads to a teen party to save the life of a young football star. Jordan and Kenny treat a beauty queen in severe distress. Topher makes a decision about his job.

A downtown gas explosion sends dozens of casualties to San Antonio Memorial Hospital.

Jordan and Krista offer roadside assistance to a motorcycle crash victim.

An injured skydiver is rescued, but there's more to the case than meets the eye. Meanwhile, the night-shift staffers treat an electrocuted janitor, then scramble to save his wife and children when they fall ill to life-threatening symptoms; and Paul learns about his limitations as a doctor.

A patient arrives with radiation poisoning, spinning the night shift into chaos and putting it into lockdown. Meanwhile, staffers speed to a serious car crash, where they discover an injured police officer, TC's troubled sister-in-law visits, and a former patient harasses Jordan.

As a thick fog descends upon San Antonio, the doctors must improvise to save the victims of a car crash; Topher, Drew and Kenny treat siblings injured in the fog.

T.C. discovers his sister-in-law's complicated history after he treats her for a fall down stairs.

A building collapses during a rodeo; a severely injured cowboy exhibits strange symptoms; Scott causes a serious car accident.