Yes. Nurse Carol Hathaway (Julianna Marguiles, Snakes on a Plane) has been in ER for six seasons altogether. Her lover, Dr. Doug Ross (George Clooney, The Perfect Storm), left earlier on in season 5. Carol missed him terribly, but did not fully convince herself to move away. She decided to stay. But, a mourning and grieving father that lost his wife explained to Carol that everyone has their soul mate. There is one person that we should spend the rest of our lives with.
That statement convinces Carol fully to quit her job at County General, board the first plane to Seattle, Washington, and reconnect with Doug for a permanent love relationship and possibly even marriage. So, Carol does leave ER at the end of this episode, but returns along with Doug in the final season of ER in early 2009.