As a storm soaks Chicago, Weaver and Gallant race to save a pregnant woman trapped in a crashed ambulance surrounded by live power lines. Carter's grandmother arrives with a mysterious injury and a morbid link to a hit-and-run victim, and Greene treats a teen taking the fall for losing his baby brother in a flooded river. Meanwhile, Benton's hopes of winning custody of Reese are dashed by a fateful DNA test, Cleo ends her days at County General, and Nicole gives Kovac bad news after being busted for burglary.