Oh, heavens, plot. I'm pretty good at getting into plots, much worse at getting out of them, and plots which you're almost required to solve by the hero being very clever - which is to say, anything featuring Miles - are the hardest thing of all. I expect this goes a long way to explaining why the most popular stories to write are the ones where the (action/adventure/mystery/intrigue) plot, if any, takes a firm back seat to the emotional plot. (She says, looking at a fic where the action plot is fine but figuring out the emotional plot is almost impossible...)

Readers, of course, tend to like an action plot along with the emotional plot.