Is the writer ever really in control of the characters? -- Sonny Manou
Never. Or perhaps I should say that if you are in complete control of the character, then that's the mark of a poor writer.
Whoa, you say. Back up there, Hoss. The writer should always be in control. Who else is putting the words on paper or typing them?
Sure. You never physically give up control of your story, but you have to intellectually (or perhaps spiritually for those inclined to such esoteric understandings of the craft). If your characters don't take over at some point and tell you what they will and won't do, then they're only cardboard cutouts that you are moving across a plot -- not genuine, living, breathing characters. They become little more than the literary equivalent of the old Colorforms toy sets or Flannelgraph displays from 1950s Sunday School.
At some point strong, well-crafted characters should and will take over your plot outline and tell you what they'd do in a given situation. Perhaps you wanted your heroine to walk into the dark room, but suddenly she tells you, "No way, buddy! I'm too smart for that dangerous notion."
So, as the writer you have to out-think her. You have to figure out what it will take to make her enter that dark room. The cry of a child? A gun at her back? Guilt from a friend who once called her a coward in front of a man she loved? Whatever. But YOU have to outsmart her.
To outsmart your characters you have to know them intimately. That's the real reason you need to develop your characters, so you have the ability to outsmart them and write around what they want to do, not to merely move them like robots in your beautiful and amazing plot.
I think the mark of a gifted storyteller is the willingness to let the characters wrangle control of the small things from you so that you can concentrate on the big things of getting them from point A to point B in a way that rings true to them.
As always, these are just my thoughts on the matter. Your mileage may vary.