Dr. Addison Montgomery-Shepherd is a world-class neonatal surgeon on the television series "Grey's Anatomy." She first met Derek Shepherd (Patrick Dempsey) when they were in medical school.They both became successful doctors with their own practices in New York City. This strained their marriage and Addison eventually had an affair with Mark Sloan (Eric Dane). This led to Derek ending their marriage and moving to Seattle to work at Seattle Grace Hospital. She began a relationship with Mark but that ended when he cheated on her. She then went to Seattle Grace Hospital to try to rekindle her relationship with Derek.
Despite still being angry with her, Derek agrees to try again, choosing her over Meredith. However, Addison finds out about his continuing feelings for Meredith and is not happy. At this point, Mark comes to Seattle Grace from New York to try to make amends with Addison. Addison eventually finds out about Derek's affair with Meredith and this makes her pursue a short-lived affair with Mark.
Addison initially has a strained relationship with her surgical intern, Alex Karev (Justin Chambers) and put him on her service so she could punish him. She starts to develop an attraction to him leading to them sleeping together. Afterward, she realized that he does not want to pursue a relationship. She begins to feel alone at Seattle Grace, so she visits an old friend in Los Angeles. She eventually leaves Seattle to work with her friend's practice in Los Angeles.
"I've total respect for you and your... midwifery skills? Is that even a word? Midwifery?"
"I'm changing my life. Now I can walk away angry or I can walk away with your blessing. Either way Richard: I'm going."