Maya and her unborn baby are fighting for their lives on the operating table, and Addison, Amelia and Fife try everything humanly possible to save them. Meanwhile, Sam operates on an incoming crash victim and later makes a grim discovery; Cooper makes an ill-timed but valiant effort with Charlotte, and the staff’s world gets rocked by an unexpected death.
Naomi begs Fife to use his still experimental treatment to help William's advanced ALS. Violet and Amelia treat a woman with a brain tumor, while Sheldon decides to vie for Charlotte's affections.
After Violet files for joint custody of Lucas, an embittered Pete voraciously fights back by hiring a tough attorney for the trial, forcing their fellow friends and co-workers to choose sides and have their personal lives dragged onto the stand and into the public eye.
After her open-ended escape to Costa Rica, Violet has finally returned home and to the practice. Everyone treads a little lightly around her, especially Pete and Addison who have mixed feelings about Violet's desire to reconnect with Lucas. Meanwhile Amelia butts into Sam's personal life, pointing out that he can mend hearts in the OR but can't seem to do that for himself; and Sheldon encourages Charlotte to reconcile with Cooper, while Cooper deals with a young patient who eats everything in sight.
When famed neurosurgeon Dr. Ginsberg and her team pay a visit to St. Ambrose to save the life of Kayla, Addison is shocked to see Amelia Shepherd - Derek's younger sister on the team. But Amelia's presence causes strife between Addison, Sam and Pete when she claims she can save Kayla's life after Dr. Ginsberg declares nothing can be done. Meanwhile Charlotte seeks from Cooper's with a sex education seminar for the elderly that only leads to more tension between the two, as they try to figure out how to work together.
A husband's decision to pull the plug on his pregnant wife is overruled by a judge, forcing the hospital to keep her on life support until the fetuses she is carrying as a surrogate are able to survive. Meanwhile, Naomi feels betrayed after learning of Sam and Addison's feelings for one another, and she turns to Dr. Fife for support while William is away on business. And unable to cope with the tension, Addison takes the day off with Pete and Lucas.
When Addison's patient and the life of the three unborn babies she is carrying as a surrogate hang in the balance, Sam's new girlfriend, Vanessa, and Addison are sharply divided on the course of treatment. Meanwhile Cooper seeks Sheldon's help with a young patient, but their personal quarrels over Charlotte get in the way, and Naomi has a dilemma of her own between William and an unexpectedly charming Dr. Fife.
Things get too close for comfort when Addison, Pete and Sam must come together on a complicated case involving a dad-to-be who comes down with tuberculosis and threatens the future of his new family. Meanwhile, with Violet still gone on her Costa Rican escape, Sheldon takes over helping one of her patients, Natasha, to get over her crippling fear of flying, and Naomi finds herself in a bit of a love triangle of her own.
It's Maya's wedding day and while Violet helps Sam prepare, a furious Naomi still refuses to take part as she works with Addison and Pete to save a premature baby. Meanwhile, Cooper becomes suspicious of Charlotte's new boyfriend and thinks that he may be abusing drugs.
When Naomi refuses to help plan Maya's wedding, Sam convinces Violet to help her. Meanwhile the tension between Addison and Sam deepens when they treat a suicidal patient and Cooper and Pete treat a girl with a questionable bite mark.
Addison and Cooper are counseling a couple who must pick a child to save with their newborn's cord blood. Meanwhile Dink wants to marry Maya.
Maya shocks Sam and Naomi, while Pete and Fife disagree on patient care.
Desperate to help his pregnant daughter, Mark (Eric Dane) follows Addison back to Oceanside Wellness, Dell and Naomi struggle to raise their children under the same roof, and Violet and Cooper heatedly disagree on how to treat a patient on.
An explosion at Dell's house lands Betsey and Heather in the hospital. everyone is pushed to the limit in trying to save their lives. The tensions between Addison and The Captain rise even more when her mother, Bizzy, shows up and a shocking family secret is revealed.
Addison performs a complex utero surgery, proving not only her talents to her father but giving them some common ground. Sam and Naomi deal with have a family crisis when they discover Maya is growing up way too fast. Violet does the unthinkable.
While Addison deals with the unwelcome arrival of her father, Cooper is arrested because he refused to cooperate in a case involving a longtime patient. Meanwhile, Pete will stop at nothing to keep a terminally ill patient alive for as long as it takes for him to meet his new daughter.
Addison and Sam go for a hike in Malibu, they come across an expecting couple trapped in their car after an accident, they then perform urgent field care. Charlotte, Cooper and Violet treat a newlywed who, on his wedding night has taken too much Viagra. Pete and Sheldon go out to a bar together and end up falling for the same girl.
The doctors venture into controversial territory when an unexpected new hire at Pacific Wellcare causes Naomi to struggle with the idea of genetically designing babies and Violet makes a sudden decision to try electric shock therapy on a patient. Meanwhile Addison somehow finds herself alone and with a cat.
Katie Kent is apprehended and on trial. Violet is asked to testify against her attacker, but she struggles with whether or not she can face her attacker in court. Meanwhile a serious complication threatens the fetuses of two of Naomi's former patients and Charlotte is determined to convince Addison, Sam and Cooper to let her join Oceanside Wellness Group.
Addison, Sam and Cooper treat the sick child of a homeless teen mother they met while volunteering. Meanwhile Violet has trouble relating to her baby when her feelings about her attack resurface during counseling of a rape victim who is now pregnant, and Cooper's financial woes catch up with him when he's asked to help buy out Naomi's share of the practice.
Miranda Bailey brings a kidney transplant patient to Los Angeles, and Addison and especially Sam is pleased to see her. Addison's consequences of her emotional affair with Noah catch up with her. Sheldon and Pete finally discover who the father of Violet's baby.
Violet is physically recovering from her violent attack at home, but the emotional trauma she suffers from isn't going away, despite the best efforts of Pete and her other friends to help. Meanwhile, Addison and Naomi try to mend their tension-filled relationship, as Sam and Cooper treat a father, who has allegedly attacked his family, after he is stabbed by his wife.
When Pete discovers Violet clinging to live following a violent attack from a patient, he rushes her to the hospital where Addison and Naomi work together to save her life. Meanwhile, the location of Violet's baby are still unknown.
