ALL IN ONE DAY, BESIEGED ABBY GETS A LETTER, A LECTURE -- AND A LESSON IN EXASPERATION -- Abby's (Maura Tierney) frustrating day gets worse when she gets a special "Dear John" letter from Dr. Carter in the Congo while her fellow nurses threaten a walkout and her opinions are ignored -- especially when she is chastised as she seeks to inform a teenaged girl (as Ellie, Stephanie Lineburg), with failing lungs and heart, that her life is in grave danger. Elsewhere, Dr. Romano's (Paul McCrane) mood gets nastier when he is fitted with an antiquated hook for his missing arm and he takes out his rage by firing several much-needed nurses. In addition, three new second-year residents join the staff -- including the self-assured Dr. "Coop" (guest star Glenn Howerton). Dr. Pratt (Mekhi Phifer) uneasily meets Dr. Chen's (Ming-Na) old-fashioned parents for dinner, and the playful Dr. Dorset (guest star Bruno Campos) makes an impression with his style and substantial skills. Laura Innes, Alex Kingston, Sherry Stringfield, Sharif Atkins, Goran Visnjic and Parminder Nagra also star. TV-14