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, the only advanced surgical care hospital in Southern Afghanistan. Perched at the edge of the airfield, 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’s acutely conscious of his inexperience. They both get off to a rocky start: it’s humbling for both of them 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, falling shrapnel and wave after wave of 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.

Rebecca is nearly run over by a pickup 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 bacterial infection, it becomes evident that the team is dealing with a highly contagious and antibiotic-resistant strain. They have no idea what it is, where it came from, or how to stop it from spreading as their patients continue to deteriorate. Colonel Marks is left with no choice but to quarantine the OR, ICU and the recovery room - the Role 3 medics are forced to do surgery in the dining hall. If they don’t get it under control fast they won’t be able to treat the incoming wounded. Meanwhile, Rebecca accompanies Pedersen off base to the Women’s Clinic where they find a local in dire need of emergency life-saving surgery.

Rebecca depletes the blood supply while she and Bobby operate on a soldier with severe gunshot wounds, forcing Colonel Marks to call for a walking blood bank. Pedersen questions the soldier’s buddies about the circumstances that lead to the shooting, but their stories don’t add up. Simon rekindles a relationship with an old flame - an attractive photojournalist on assignment. Marks appoints Rebecca as morale officer, whose primary duty is to plan the weekly staff party on the base. Reluctantly, she rises to the occasion and, with the team’s help, orchestrates a shindig complete with Western theme, campfire, food, music, dancing and a mechanical bull. Vans discovers he has a knack for more than just translation.

When Simon learns the medevac helicopter has to make a routine supply run, he hitches a ride to the farm he bought from an Afghan family which is en route. Plans go awry when the chopper’s pilots spot white tracer fire and they have to make an unexpected stop to pick up an injured US Army soldier with multiple shrapnel wounds. Meanwhile, one of Rebecca’s patients -- a Romanian civilian -- suffers a brain hemorrhage and emergency neurosurgery becomes vital to his survival. When Simon can’t get back in time to perform the surgery, he must talk Rebecca through the operation via cell phone from the medevac. Bobby and Pedersen evaluate a high-ranking US Air Force officer experiencing *insomnia – the officer has a pending mission that is critical to the Air Force’s strategic operations. No time for rest, Marks deals with an overheating CT scanner, an AWOL surgeon and delivering an unfavorable diagnosis.

A civilian wedding party is caught up in Taliban crossfire and the Afghan groom and some of the guests are brought in to the Role 3. Pedersen heads to the clinic off base to help the wedding party’s female victims and Rebecca initiates a search to find the bride. Bobby exercises his authority as Captain and attempts to ground a Sergeant intent on postponing medical tests in order to accompany his men on a mission. Bobby impresses Marks on a medical conference call. Rebecca and Bobby participate in Pedersen’s group therapy session, leaving Rebecca feeling vulnerable when she over-shares. Marks receives a worrisome call from home and confides in Pedersen.

Seven soldiers, who are brought into the Trauma Bays, anxiously wait for the arrival of their lucky charm, 19-year old Private Henry Flax. When the Private’s entire unit survives their injuries without complications, Marks acknowledges lady luck and miraculously, the new CT scanner arrives. Rebecca tries to fulfill Flax’s dying wish by rewriting the protocol for organ donation. When Nurse Suzy Chao is assigned to help Bobby with his research, she develops a crush on him. Rebecca reveals to Simon that she is jealous of Bobby’s recent success and discusses her feelings with Pedersen. Rumours about Simon circulate when he receives an unusual number of calls from England. Meanwhile, an attractive Canadian Forces Warrant Officer falls hard and fast for Pedersen.