Amy Whitfield is the easiest person in any room to like, which is a dangerous thing to be. Twenty-six, white, an MBA candidate at Columbia, a restaurant server by day and a disciplined, unbreakable, if a bit half-hearted, dominatrix on the few nights that pay for the rest, she is the kind of competent that makes hard things look easy. She never breaks character, whether in the classroom or a three-thousand-dollar-a-night midtown hotel room. She is thinking about giving up the night work as graduation comes into view. She is the person you most want to come out of this all right. But she doesn’t.