Previously on ER: Susan let Luka know that it wasn't necessary to "boff [a] patient's mother in the storage closet." Elizabeth told Romano she was sorry, and Romano asked if he was sorry about her arm or sorry that she wasn't there. Weaver made Abby the nurse manager whether she liked it or not, which doesn't quite seem legal, but whatever. I also wanted to note that all of my medical knowledge comes from watching this show, so that means I don't know much, and you'll see a lot of lines like, "Kerry orders some drugs" or "Luka orders some procedure." I'm sure that the very knowledgeable people on the forums can help you out if you need more specific information than that.
Elizabeth conducts surgical rounds with her medical students, one of who is in that commercial I hate about the lawyer with the MasterCard who is going to use his cash-back bonus to buy an engagement ring someday. Anyway. Elizabeth is peppering them with questions about symptoms, none of which they can answer. It's 5:07 PM on Halloween. Elizabeth resorts to giving them the first letters of the answers for which she is searching. When they guess "neck" and "navel" instead of the correct answer -- "nail bed" -- she sighs in frustration and tells them to go home, and return for rounds the next morning at 7 AM. She murmurs to herself, "So much for the future of medicine," because she was apparently never a clueless medical student. She announces that she's going trick-or-treating, and that Ella is going to be a cow. A nurse asks if Ella was a cow last year, and Elizabeth says that Ella was Dorothy, she was the Cowardly Lion, and Mark was...she pauses here, realizing that Mark isn't around anymore. Come on, what was Mark? A flying monkey? A member of the Lollipop Guild? Toto? No, apparently Mark was the scarecrow, which is kind of funny considering that the scarecrow lacked a brain and Mark died of a brain tumor. The nurse is like, "Sorry I asked." Elizabeth says she's going to be a farmer this year. A nurse stops Elizabeth on her way out and says that her medical student -- the one who didn't show up today -- called. His name is Nathan, and he'll be there in a few minutes to speak to her. Elizabeth says that it's too late. The nurse says that Romano also wants to speak with her. Elizabeth wants the nurse to tell Romano that she couldn't be found, but the nurse is holding a phone, and Romano's on the line. He yells, "I heard that!" The nurse hands Elizabeth the phone.