This week, Lucy treats a man who she suspects may have psychiatric problems, Carter returns to his peak know-it-all phase, Abby gets a lesson in end of life care, Romano operates on his best friend, Mark accidentally arranges a double date for Valentine's Day, Carol, Luka, Corday, and Benton all try to save two parents after a bad car crash, and Chen and Malucci bicker over the best course of treatment for a cancer patient.