following the plot or losing it.

When writing a short story I plot out the action. Who is doing what to whom, where it is happening, what is happening next from the top of the arc. All planned out...and then....as I'm writing things begin to go awry. Suddenly the plot takes a left turn and and the emphasis changes. Is it better? Maybe? But what of the story I started with in the beginning? Try as I might it just isn't happening.
So this is when the character writes the story.
My thoughts are that once you have the character firmly attached to the action and you know how they will react, what they are likely to say and why then the plot evolves. It's not a hijack more of evolution.
I could corral the story in and write the original idea, but I kinda like the way the new twist is working.
So my character has evolved in 1800 words and moved the action along to a different conclusion.
And I thought I was in control!
Perhaps this is what writing is all about. Being adaptable. Being able to bend. And to top it off I can't get the character out of my head. He is there all the time.
Does the character write the story? Or...
and what do other people say...
wikipedia story arc
plotting
plotting your story
plots