The fourth season of Private Practice premiered on September 23, 2010, and concluded on May 19, 2011. The season consisted of 22 episodes.
Pete and Violet prepare for their wedding day; things take a surprising turn with Addison and Sam; despite disagreements, the doctors come together to mourn the loss of Dell.
Violet and Cooper make changes to their friendship to appease their significant others; Pete and Cooper argue over a patient's (Justine Bateman) marijuana use; Addison debates going public with her new romance.
The man responsible for killing Dell and endangering Maya's life comes to the clinic with a heart condition; news of Addison's new romance is not received well.
Emotions are stirred up at the practice when Dell's daughter arrives; a pregnant woman experiences chronic pain.
Addison butts heads with a new oncologist (Cristian de la Fuente) while treating a newborn with a malignant tumor; Pete is uncomfortable when Violet tries to help a parolee.
Sam and Addison disagree over the treatment of a comatose patient who becomes pregnant; Charlotte and Pete face an ethical dilemma when a patient with HIV is in a serious car accident.
Pete finds Charlotte bloodied and bruised in the halls of the hospital, but only Addison learns the full extent of her injuries.
Charlotte suffers in silence after the assault; Addison tries to keep that night's events a secret.
Despite how Charlotte is choosing to deal with the aftermath of her sexual assault, her fellow doctors think they know what's best, teaming up to pursue criminal charges against her attacker. Pete gets a surprise visitor, his estranged brother, who has come to ask Pete to help release their sick mother from prison.
Cooper is outraged when he gets bad news about Charlotte's sexual assault case.
Addison's mother, Bizzy, aggressively demands her daughter do whatever it takes to save her partner from dying - including working with Dr. Rodriguez once again. Meanwhile Amelia and Pete's medical consultation is complicated when a patient's wife and his mistress disagree on the course of treatment, Charlotte and Cooper try to be intimate with each other again, and Violet considers publishing a personally-revealing book she's written.
Addison plans Bizzy and Susan's wedding while trying to keep her distance from the overly flirtatious Dr. Rodriquez. Sam is concerned about the care his longtime patient is receiving, and Sheldon refers Charlotte to his mentor and friend for psychiatric help.
Charlotte's attacker, Lee Henry, arrives at St. Ambrose Hospital, injured by his girlfriend and in need of urgent care, and Sam and Charlotte must decide whether or not to save his life. Meanwhile, Susan's health takes a turn for the worse, and Addison's mother, Bizzy, begs her daughter to do everything in her power to help.
After tragedy strikes the Montgomery family, Addison goes home to Connecticut and Sam and her friends decide to join her. Meanwhile, Sheldon and Violet clash when Sheldon's death row patient confesses to a crime that his wife, one of Violet's patients, believes he didn't commit.
Charlotte and Cooper look to forgive each other after revealing secrets during couples therapy, Violet seeks the forgiveness and approval of her fellow doctors after they learn her novel-in-progress will make all of their personal lives public, Sheldon treats a patient who claims to have multiple personality disorder, and Sam and Naomi team up on a case involving a pregnant teen with Down's Syndrome.
A couple wants to harvest eggs from their unborn child who is not going to survive, and the doctors cannot agree what the right path is; meanwhile, Amelia tries to comfort a friend while waiting for test results for Huntingtons disease.
Violet's book launch party has finally arrived but Sheldon finds himself attracted to the doctor who criticized her book. A surrogate under Addison and Pete's care is caught in a complicated love triangle. Cooper and Sam must convince a family that their son's health must take a priority over his sports career.
Pete suspects that his brother Adam may be responsible for their mother's illness. Meanwhile, Violet discovers quite by chance that Sheldon is dating Marla Phillips, the doctor who panned her book, and who Violet considers as her archenemy. Cooper's patient is a musical prodigy with a debilitating brain tumor.
Katie threatens to take legal action against Violet for "breach of confidentiality," and although Violet feels that she hasn't done anything wrong, she soon realizes she'll have to defend her actions to more people than just Katie. Meanwhile, Cooper suspects that Charlotte may be hiding some lingering feelings for ex-husband Billy, only to find out that Billy has been hiding some feelings of his own.
The day has arrived for Cooper and Charlotte to marry, but not everyone is in a celebratory mood, leading the couple to second-guess their wedding plans. Meanwhile, the doctors of Oceanside Wellness are torn between the future of their practice and protecting one of their own, as an investigator is sent to question them about Violet's breach of confidentiality case.
When Betsey returns to the ER for a second visit, the concerned Oceanside doctors start investigating the foster family. Amelia struggles to stay sober while Naomi announces a life changing decision affecting her family.
The fate of Oceanside Wellness is on the line as the doctors decide if it's time to dissolve the practice. Addison's new admirer makes an enticing offer and things hit close to home for Charlotte with her latest case.