The Seaside Wellness group stages an intervention for a defensive and volatile Amelia, who has resurfaced after disappearing on a 12-day drug binge with her boyfriend, Ryan. During the intervention, Amelia mercilessly attacks her friends one-by-one, and Addison, in particular, has trouble seeing her sister-in-law in her present condition.

When Amelia goes into labor, the Seaside doctors - even those she pushed away -- come to her side as she faces the hardest decision of her life. Meanwhile, after Pete finds himself in life-changing trouble, he and Violet realize what they mean to one another, and Addison is faced with a choice.

Amelia makes the hard decision to enter a rehab facility, and finds strength through an 18 year-old girl, as they both go through the painful detox process. Meanwhile, Cooper’s strengthening bond with his son is tested by his allegiance to a patient in need, Pete and Violet’s marriage reaches a tipping point, and Addison collapses from her rigorous fertility treatments.

Cooper and Charlotte take Erica to Seattle Grace to meet with Derek, Lexie and Amelia regarding a very risky surgery; Scott tells Violet that he would like to take their relationship to the next level; and Addison finds herself caught in the middle of Sam and Jake's fight about a patient. Meanwhile, Sheldon warns Sam to be cautious as he deals with the return of his sister, Corinne.

As Erica's condition worsens, Cooper and Charlotte try to prepare Mason, who's in denial, for the worst; Violet and Pete find that they still have feelings for each other; Addison encourages Amelia to embrace her impending motherhood; and Sheldon and Jake treat a pregnant woman who was jailed for killing her other two children.

Violet steps in to the middle of a dangerous situation.

Sam tries to take care of his sister, Corinne, but her mental condition makes that nearly impossible; Sheldon learns that Amelia has life-changing news; the flirtation between Addison and Jake continues, and Cooper rejects Charlotte's suggestion to seek outside help with Erica's care.

Cooper, Sam, Amelia and Charlotte try to save Pete's life after his heart attack; Addison's desire to have a child leads to a surprising encounter; Sheldon hopes to help Amelia with her alcohol addiction.

Cooper receives the surprise of his life when a woman from his past arrives at the practice; Addison consults her patient, Jodi, who is eight and half months pregnant and suffering from severe memory loss after a traumatic car accident; and Sheldon and Violet clash when their patient, Jodi's husband, Zach, considers leaving his wife and taking the baby with him.

Charlotte's painful memories of a horrible tragedy are triggered as Amelia continues her downward spiral; Addison takes one step closer to motherhood when she finally chooses a sperm donor; Cooper faces a difficult decision when he realizes his patient's parents have been drugging their son in an effort to control his supposed ADHD; and Pete's trust issues prevent him from repairing his fragile relationship with Violet.

Amelia’s drug addiction spins further out of control as she plays hooky from work with a new fling, starts writing pill prescriptions for herself, and has a run-in with the cops; Addison and Jake are at odds when they must make the impossible choice between donating their patient’s organs or saving the life of her healthy, unborn baby; Violet begins working at Seaside Wellness again, and Cooper, Charlotte and Mason begin to form a family bond, much to Erica’s chagrin.

Pete, Violet, Sam and Addison adjust to their new, singles lives in different ways. Addison questions how much she wants a baby and confides in Jake, Violet considers an offer to go on a date with a young, hot paramedic, and Sam and Pete have a bachelors' night at a local bar. Meanwhile, Charlotte faces a personal, ethical dilemma when Amelia uncovers a secret about Mason's mom, Erica, and Sheldon refuses to bend to the pressure when an old friend from the police force wants him to rubber stamp a fellow cop suffering from PTSD.

Sheldon counsels Sam's friend, Rick, an Army veteran suffering from PTSD who harbors a secret sexual trauma; Erica and Mason are involved in a car accident that forces Cooper and Charlotte to further come to grips with their future; Violet and Pete struggle to navigate life after marriage when he finds her kissing Scott; and Addison and Jake attend a medical conference they won't soon forget.

Sheldon warns Sam that he may be in over his head when he insists on releasing Corinne from the hospital and caring for her at home; a badly beaten Scott arrives at the ER and is placed under the care of Pete; Amelia is encouraged to make a decision about her unborn child; and Jake's daughter grills him on his love life when he visits her at college. Meanwhile, Erica's health takes a turn for the worse.

Pete and Violet enter marriage counseling to help patch up their relationship; Amelia shuts down emotionally and avoids her peers upon hearing some devastating news; Addison adjusts to the new man in her life, and Charlotte and Cooper struggle with Mason when he refuses to speak to them. Meanwhile, Violet becomes suspicious of the sister of one of her patients.

Sam finds his estranged sister, Corinne, in jail, heavily medicated and near-catatonic, and brings her to Sheldon for help; Erica begins secret treatments for her cancer and refuses to let Cooper and Charlotte tell Mason; Cooper, Pete and Addison treat the baby of a drug addict; and things between Violet and Scott continue to heat up in the bedroom.

Addison, Pete and the team treat an illegal immigrant facing deportation who self-induces her pregnancy so that her child will be a U.S. citizen; Cooper and Violet work with a young girl who has gender identity disorder - and with her parents -- and Violet wants to continue therapy with Pete before they begin dating again.

While interviewing potential replacements for Naomi, the doctors at Oceanside Wellness don't understand Addison's resistance to hiring Jake Reilly; Cooper disregards the law as he tries to help a young, sick patient.

A woman without a uterus asks Jake and Addison to help her have a baby; Amelia treats a woman with Parkinson's disease who is habitually unfaithful; Violet struggles with her life as a stay-at-home mom.

Addison begins in vitro fertilization treatments with Jake's help, unbeknownst to Sam, Amelia is deeply conflicted when her terminally-ill friend, Michelle, asks her assistance in her suicide, and Sam and Violet contend with a patient who refuses his anti-psychotic medication.

Cooper struggles with whether or not to punish Mason after he catches him stealing; Pete and Violet find it hard to split time with Lucas now that they're living apart; Addison makes changes in her home life to prepare for a potential new baby; Violet and Jake work with two women and a man involved in a polyamorous triad; meanwhile Amelia returns to the practice and realizes how badly she hurt Sheldon when she was abusing drugs.

When a patient's partner and father are heatedly divided on his health care, Pete makes a decision that impacts everyone, including himself; meanwhile, Jake offers strength and experience to Amelia when he suspects she's being tempted to substance abuse, Sheldon and Violet treat a family concerned about the father's new sexual appetite, and as baby Henry draws Addison and Sam closer, they struggle to define their relationship.