When a torrential rainstorm pounds Chicago, patients deluge the emergency room while Weaver speeds to an accident site. There, she finds a pregnant woman, Vicki lying injured inside a wrecked ambulance while live power lines spark. Fourth-year student Michael Gallant makes a dangerous decision in order to help. Meanwhile, a nervous Benton receives the lab reports that indicate whether or not he is Reese's father; Kovac's new girlfriend, Nicole gets into trouble and gives Kovac some unexpected news; Carter's grandmother, Millicent, is wheeled in after she breaks her hip in a hit-and-run car accident that injured a young woman, Jill; and Greene tends to a guilt-ridden boy, Daniel Pendy, who feels responsible for the disappearance of his younger brother in a flooded river in which they were playing. Recurring guest star Lisa Vidal appears as Sandy Lopez.