In the classic drama's 150th episode, a multi-car train accident scrambles the ER and Drs. Kovac, Carter and Corday are overwhelmed by the carnage at the site as they work to save an impaled mother, her young son and a trapped firefighter -- until the pregnant Corday begins to suffer painful contractions. Back at County, Dr. Benton tries to salvage a victim with a shredded aorta and even helps Carter with a tricky amputation over the phone, all of which leaves an observing med school applicant wide-eyed. Meanwhile, the bloody mayhem prompts Kovac to recall the harrowing loss of his own family and he confronts his torment with the terminally ill Bishop Stewart.