This week: Corday's post-op deaths trigger a criminal investigation, Susan cares for a pair of college students with a very contagious disease, Carter tries some alternative methods to help his back pain, Luka treats a homeless man, Rachel isn't very good at babysitting, Benton gets stuck in the middle of an argument between Jackie and Roger, Abby gets asked out by a patient, and Mark treats a mom and daughter who were caught in a fire.