Plot summary
When William White passes away, Naomi decides that they should combine the two practices. Charlotte and Pete decide that Violet and Cooper need to spend less time with each other for both of their relationships to survive. Charlotte gets Sheldon to help her with a patient who is trying to get a sex change, but gets angry when Sheldon denies her patient the surgery. Addison decides that she and Sam can't keep their relationship a secret, and tries to tell Naomi, but doesn't until the end of the day, resulting in Naomi telling her to back her up with the merger.
Addison also pushes Amelia to go visit Derek, eventually buying a plane ticket for her to go to Seattle. Pete and Cooper go head to head when Pete's patient starts giving her autistic child her medically prescribed pot. Cooper and Violet decide that they should see less of each other so that their significant others don't feel left out anymore.
Credits
Adapted from Wikipedia contributors, Private Practice season 4. HTML formatting and reference markers removed.