Halloween night finds the ER awash with allergic or otherwise incapacitated children. Kerry tolerates a visiting candidate for chief while she waits for the official vote. Romano operates on an 11-year-old girl and finds she's genetically male. Carter breaks up a dorm party, but Lucy and a few stragglers remain - with unfortunate results. Mark learns that Jenn's moving to St. Louis and taking Rachel with her. Mark and Carol treat a pregnant schizophrenic.