Nurse Veronica Flanagan Callahan (Taylor Schilling) has just returned to Mercy Hospital from a tour in Iraq and knows more about medicine than all of the residents combined. She works with fellow nurses Sonia Jimenez (Jaime Lee Kirchner), who turns the heads of everyone in the hospital, and Chloe Payne (Michelle Trachtenberg), a native newcomer who learns to deal with the difficulties of working in a challenging and sometimes unsettling profession.