Life. Death. And chaos. It’s all in a day’s work in the overburdened Chicago ER. Season 7 brings a busload of sickened school kids, a crazed gunman whose shooting spree has already claimed 19 victims . . . and, of course, the guy in the opossum outfit who bit the man dressed as a kangaroo! But for the dedicated doctors and nurses, the life-and-death drama of their professional lives doesn’t seem to let up when they’re off-duty. Abby Lockhart faces a difficult reunion with her mother (guest star Sally Field), a turbulent woman suffering from bipolar disorder; while Carter makes a harrowing return from detox; Benton struggles against the iron grip of Dr. Robert Romano; Kovac confronts a mugger; Weaver confronts her sexual orientation; and Chen refuses to reveal the father of her child. Meanwhile, Drs. Greene and Corday get married — only to live under the looming shadow of Greene’s impending health crisis. Excitement, drama, and suspense are on call in the ER.