Nurse Veronica Callahan has just returned to Mercy Hospital after a tour of duty in Iraq. Though not afraid to bend the rules in order to save a life, her outspoken attitude might cause her to lose her job. While trying to get over her broken marriage to Mike, she catches the eye of the newest doctor, Dr. Chris Sands. Meanwhile, Sonia, Veronica's best friend, thinks she may have found the one; and rookie nurse Chloe learns the hard way what it means to be a nurse.
Veronica and Mike try to put the pieces of their marriage back together, but after deciding to move in together they realize their house needs more work than their marriage. At the hospital, Veronica has a hard time staying just friends with Dr. Sands; Sonia has Nick Valentino help her identify a Jane Doe; and Chloe helps a patient everyone else has given up on.
Veronica is determined to save the sole survivor of a horrific nightclub fire. Chloe tries earning the respect of her co-workers and the affections of a workplace crush. Meanwhile, Sonia and an energetic new female doctor butt heads and Dr. Harris romances a mysterious beauty.
Mike's pressuring of Veronica to start a family has her deciding whether to end her affair with Dr. Sands. A pair of feuding patients has Sonia acting more like a marriage counselor. Chloe is thinking about taking her crush on Dr. Sands up a level.
Veronica attempts to save a pregnant woman who was involved in a car wreck. Dr. Harris wants a meeting to determine whether Veronica should remain at Mercy Hospital. Meanwhile, Sonia tries to help out a patient who sleep walks.
Veronica takes advice from a courageous cancer patient by getting enough nerves to admit to her husband that she's had an affair. Elsewhere, an experienced patient gives relationship advice to Sonia, and Chloe plans a reunion with her ex-boyfriend.
Veronica decides to attend a PTSD support group all while dealing with her marriage and her father's Alzheimer's disease. Meanwhile, Sonia helps a mother with her decision to up her newborn up for adoption; and Dr. Harris suffers a bizarre injury, leading Chloe to have to deal with one of the most difficult types of patients -- doctors.
Veronica helps a patient after a terrifying experience on an operating table. Meanwhile, Veronica begins to think that Mike has begun dating again. Sonio tries to find a patient's next of kin, but instead comes across a secret that will change the young girl's life forever. Elsewhere, Chloe is forced to moderate a family feud when a family can't agree on the course of action for their dying father.
Three college students are admitted to the hospital with meningitis they contracted while involved in a love triangle, which leads the staff to make comparisons to Veronica's own complex love life. Meanwhile, Chloe agrees to help a bride-to-be with her wedding plans when she is admitted to the hospital with the flu, but receives a much dire diagnosis. Sonia helps a defiant hand transplant patient who wants to have his hand amputated when he learns that it belonged to a pedophile.
A newlywed cancer patient undergoes a risky course of treatment and Chloe struggles to help her doting husband cope. Meanwhile, a man wakes up after ten years in a coma and decides to confront the woman he loves, prompting Veronica to spring to action in her own love life. And Sonia gets a taste of how the other half lives when she cares for a wealthy and eccentric family.
the arrival of Dr. Joe Briggs, the arrogant new head of ICU with whom Veronica promptly locks horns. Meanwhile, Veronica and Dr. Sands must set aside their own icy relationship as they try to save a boy found nearly frozen in the woods. Following the death of one of her patients, Chloe helps the grieving widower take the difficult step of leaving the hospital and Sonia continues her turn as private nurse to an upper-crust family
On Valentine's Day, Veronica's first real date with Chris takes an unexpected turn.
Following the donut shop shooting, Veronica finds herself overwhelmed by PTSD. Accompanied by a disturbing visitor, she takes off on an impromptu road trip, leaving everyone concerned. Back at Mercy, the victims of a bus bombing inundate the E.R., causing Dr. Briggs and Dr. Sands to clash over the only available operating room. Chloe battles a hangover on her second day in the E.R., Sonia struggles to conceal her infidelity from Valentino and Dr. Harris treats a patient whose injury causes her to make inappropriate sexual advances.
Veronica takes on extra shifts and rekindles her relationship with Dr. Sands in an effort to avoid dealing with her recurrent PTSD symptoms triggered by the robbery. But when she makes a terrible discovery about a young patient, her impulsive reaction shocks everyone - including her. Meanwhile, Sonia (Jaime Lee Kirchner) is confronted with an agonizing ethical decision when her elderly home-care patient announces her plan to end her own life, and Chloe gets the surprise of her life when she accompanies Briggs on a VIP house call
Veronica cares for an anorexic patient who is almost as good at denial as she is. When Sands and the Flanagan clan confront Veronica after a St. Patrick's Day binge, she considers seeing a therapist. After working with him to save a heart attack patient, Chloe softens slightly toward the arrogant Dr. Briggs when she learns why he became a doctor. Meanwhile, Sonia, still privately mourning the death of her home-care patient, is surprised to run into her ex-boyfriend at a St. Patrick's Day fair.
Veronica begins the difficult process of confronting her PTSD with her therapist. Although Sands is eager to move forward with their relationship, Veronica finds herself siding with Briggs against him in a dispute over a patients treatment. Chloe and Harris team up to help a cute college football player with a potential brain injury and Angel butts heads with an eccentric ER patient. Meanwhile, Sonia cares for two hipsters after their hair-brained attempt to win a girls heart lands them in the hospital, but their romantic gesture inspires her to make her own.
Veronica continues her therapy sessions; Chloe tracks down an ER patient with potentially fatal blood test results.
Sands and Veronica are suddenly faced with a life-changing decision; intimidated by a stalker's threats, Sonia turns to a surprising source for help.
When two boys get trapped in an abandoned building, Veronica finds herself in the right place at the right time to help them. Back at the hospital, Chloe pressures doctors to perform a risky surgery to save her comatose boyfriend from brain death, and Sonia treats a psychic patient who makes a mysterious prediction about her future. Meanwhile, Briggs tries frantically to raise the funds needed to pay off his high-stakes debt with the mafia before it's too late, and Sands considers a job offer to return to Afghanistan