"The Hardest Part" is the eighteenth episode of the fourth season of Private Practice and the 72nd produced episode of the series. It is also the 216th produced episode of the Grey's Anatomy franchise. It was broadcast on March 31, 2011.
Pete's family troubles are brought to the surface when his mother arrives at the hospital and Pete begins to suspect his brother may he responsible for her ailing health. Violet's book interferes with her ability to act as a therapist when she discovers the consequences of the entire world knowing her personal life while Sheldon continues to conceal the fact that he is now dating Marla Tompkins, the critic who paned Violet's book. Cooper and Amelia treat a young musical prodigy and come to blows over whether they should change his course of treatment to save his talent.
- "Whole New Way" - Scissor Sisters
- "This Time Tomorow" - Trent Dabbs
- "Bring On The Wonder" - Sarah McLachlan