Plot summary
Addison begins planning Bizzy and Susan's wedding. Charlotte goes to therapy, but is shocked when the therapist gives her prescriptions instead of listening to her talk. When she tells Sheldon, he is confused because the therapist is his longtime friend and mentor, and goes to find out what has happened. At dinner his friend has a psychotic break and runs off. Sam begins to worry about an old patient when he notices that the caretaker has been taking credit cards out in his name. After seeing Addison flirting with Dr. Rodriguez, Naomi tells her that she is most likely going to mess things up with Sam as she always does when things are good.
Charlotte and Cooper decide that they're both ready to have sex again after the attack. At the wedding reception, Addison finds out that Susan signed a DNR and isn't truly as well as she's been leading everyone to believe, and she eventually collapses while dancing with Bizzy.
Credits
Adapted from Wikipedia contributors, Private Practice season 4. HTML formatting and reference markers removed.