Welcome to the night shift at San Antonio Memorial, where those who work the Night Shift are a special breed. Every night is a balancing act between the heroic efforts to save lives and the hard truths of running a hospital. After a rough night, TC Callahan, a gifted ex-Army doctor, deals with a life-threatening situation on his way into work. TC’s current colleague and ex-girlfriend Jordan Alexander angles for the top job to run the night shift but she must convince their new boss Michael Ragosa that she has what it takes to bring order to the chaos. TC and Ragosa clash over hospital business matters - TC would do anything to save a patient while Ragosa has his eye on the bottom line. Later, TC and Topher are called to the scene of a nighttime crash and must deal with a dramatic injury that demands all of TC’s expertise. Back at the hospital, ER psychiatrist Dr. Landry De La Cruz consoles the brother of the wounded teen while TC performs an unusual and extremely risky surgery. TC later counsels Drew about a secret he is keeping but unbeknownst to the staff, Ragosa is hiding a secret of his own.

When a Sheriff’s Deputy is critically injured, TC Callahan faces a personal challenge and struggles to do everything to save him, even calling in a cardiac specialist over the objections of his boss Michael Ragosa. Topher and Krista assist in the delicate surgery, while Jordan works to keep the peace and keep the ER running. Paul must attend to an elderly woman with a very challenging case. Kenny deals with an injured groom who has been hiding a secret from his bride. Meanwhile, Drew and Landry are faced with a 9-year-old boy who has suspicious injuries. While they initially suspect the mother, the truth is a little more complicated.

TC and Paul are called to the chaotic scene of a nighttime hog-hunting excursion that has gone horribly wrong. One patient has lost a hand to a feral hog and another has been shot with an arrow through the chest. Topher deals with a resourceful 9-year-old girl who has come to the hospital on her own to seek treatment but soon realizes the case is far more complicated. Drew injures his hand during a MMA fight and enlists Krista to help him keep it a secret from Jordan. Ragosa seeks some family counseling from Landry and when Ragosa threatens to close down the staff hangout known as the "Tailgate," Landry helps him understand the benefits of a compromise.

The emergency room is flooded with patients from an annual Alamo reenactment. TC, Jordan and Kenny deal with a critically wounded patient who is disoriented and suffering from amnesia. The patient is also wearing a bracelet indicating he declines medical treatment, putting Jordan in a professional bind with Ragosa. Meanwhile, Drew must keep a severely wounded soldier alive while being miles away from help. Back at the hospital, Ragosa helps himself to aspirin in Landry’s office but soon realizes he has taken something very different. Topher schedules a vasectomy operation and the staff can’t resist the temptation to tease him at every turn. Jordan’s long-distance boyfriend Scott, surprises her with a visit to the hospital.

An epic storm hits San Antonio and the emergency room is awash in patients and must use their battlefield skills to deal with massive power outages. TC and Dr. Scott Clemmens race to the scene of a mudslide disaster to treat a gravely injured mother and her son. Paul rises to the challenge of caring for the boy, whose condition takes an unexpected turn for the worse. Scott considers an offer from Ragosa to join the hospital staff as head trauma surgeon. Jordan isn’t sure that’s going to work out with the tensions between TC and Scott. Landry is caught by surprise when a family member shows up at the hospital looking for money to cover his debts. She finds some needed moral support from Ragosa. Meanwhile, Topher must head out into the storm to help his wife who is stranded and going into labor with twins.

Drew is looking forward to the return of his boyfriend Rick from his overseas deployment but things go terribly wrong as a horrific crash sends badly wounded soldiers, including Rick, into the emergency room. Drew struggles to keep his relationship under wraps with TC’s help, as they both try to save Rick. TC and Scott argue over who is in charge and Jordan realizes she has to deal with some unresolved feelings for TC. Topher struggles to diagnose a soldiers illness as Krista fends off the flirtations of young soldiers in the emergency room, and Paul must contend with their good-natured teasing because he looks so young. Kenny discovers Ragosa’s online dating profile and offers to help fix it up.

When a small plane goes down near San Antonio, TC and Topher chopper out to the scene and retrieve the lone survivor. Back in the ER, they deal with his serious injuries but must fend off Milo, a menacing law enforcement officer with a hidden agenda. Paul is mesmerized by an injured exotic dancer who lands in the emergency room after falling during her performance. When her condition takes a mysterious turn for the worse, Paul, Kenny and Drew are baffled by her life threatening symptoms and must go to an already swamped Jordan for help. Krista tries to help a teenager with a serious eating disorder that her family refuses to recognize. Meanwhile, TC struggles with increasing flashbacks and the traumatic death of his brother in Afghanistan.

Topher is gravely wounded in a shootout with Milo. TC and Scott perform Topher’s emergency surgery as TC struggles to keep his increasingly troubling Afghanistan flashbacks under control. After experiencing the hostage situation, Jordan comes to understand the immense pressure that TC has been under since leaving Afghanistan. She struggles to maintain her composure when she must treat Milo, who was responsible for the shooting. Meanwhile, an explosion at a fertilizer factory sends badly burned victims to the ER and threatens to overwhelm the shorthanded staff. Krista must step up to manage a patient who is crashing. Jordan learns a devastating secret about TC.