This week: Luka is a good samaritan, Neela has second thoughts about her career path, Abby finds out if she gets to be a doctor or not, Sam leaves Chicago in a hurry, a mom and son are critically injured thanks to a high driver, Carter has issues after returning to work too soon, Kerry fights for custody of Henry, and a simple case of road rage turns into a fight for Pratt, Chen, and Elgin's lives.