Burke: You were gone when I woke up.
Cristina: I had to do a thing.
Burke: You didn't leave a note.
Cristina: Yeah I had this thing to do. You know I did this thing.
Burke: And once again...
Burke: We go to sleep. I think everything is fine and by the time I wake up you're just a little bit crazy.
Cristina: Okay, I'm not crazy. I had a thing.