A mass shooting at a cinema inundates the hospital with gunshot victims, including the shooter. Dr Rhodes faces a crisis of conscience.
Rhodes and Zanetti race to save a member of Firehouse 51, April's brother struggles during his first day at the hospital, and a woman saved from a burning building leads to a bigger mystery.
Dr Rhodes tends to two injured airplane stowaways, but their treatment becomes complicated when the Department of Homeland Security arrives.
Changing roles and colleagues prove a test for the doctors as Rhodes and Choi face new environments and problems.
Dr Halstead resuscitates a patient with stage four cancer despite the family's objections. Meanwhile, the nurses work on improving patient satisfaction.