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.

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. 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.