It's 2006: Major Rebecca Gordon, a highly-trained trauma surgeon, and Captain Bobby Trang, a brand-new doctor, report for duty at the NATO Role 3 Multinational Medical Unit at Kandahar Airfield. Perched at the edge of the airfield and built out of plywood and canvas held together with duct tape, the temporary building that houses the Role 3 shakes every time a plane takes off.

The hospital's commander, Colonel Xavier Marks, tells the newcomers to expect an experience unlike any they've had before. Rebecca thinks she can handle anything, while Bobby is acutely conscious of his inexperience. They both get off to a rocky start, as Colonel Marks points out Rebecca's mistakes and tries to build Bobby's confidence. But over the next 48 hours, as they deal with rocket attacks, flying shrapnel and wave after wave of injured and wounded U.S. Marines, Canadian soldiers, Afghan civilians and even a Taliban prisoner, they manage to rise to the challenge, even as they grow more and more exhausted. Welcome to Kandahar, indeed.

Rebecca is nearly run over by a pick-up truck full of Afghan National Army soldiers heading for the hospital. Their leader -- who turns out to be an American Special Forces operative -- carries in one of his men, delirious with a serious infection, one that neither Rebecca nor Bobby have encountered before. When another patient comes down with the same infection, the team realize they're dealing with a highly contagious and resistant bacterial strain, with no idea what it is, where it came from or how to stop it from spreading. Colonel Marks is left with no choice but to quarantine the OR, ICU and the recovery room, so that the Role 3 medics are forced to do surgery in the dining hall. Meanwhile, Rebecca accompanies Pedersen off base to the Women's Clinic, where they find a local in dire need of emergency life-saving surgery.