Even though I loosely outline my novels, the plot still has the power to surprise me. That's a good thing, because at least for me, if I know everything from the outset, I don't have enough drive or curiosity to write the story.
I feel like I'm somewhere in the middle between pantser and plotter. Writing without any framework is terrifying, but writing with too much of one is constraining.
Yesterday, one of my protagonists surprised me. Or rather, plot events surprised both me and him. It turns out there is a secret about him that he doesn't know yet and it's pivotal to plot events. And I didn't know about it until yesterday.
Now my job as the writer is to make this look both utterly inevitable and organic without being predictable at the same time. That's where gentle foreshadowing gets layered into the earlier story. Of course, my new understanding of this character changes some elements of the story as I've already told it, and I will need to catch some of the (now) inconsistencies in the revision. That's what my story problems folder is for. I keep a running list of open issues that need fixing, so I can keep moving forward with the story.
Sometimes, I can't trick my subconscious into doing that and I'm dragged back to fix the problems first. Other times, I can promise the story that I will fix them and it lets me alone.
It's a strange process, this writing of story. One that I know I'm not fully in charge of.
That's a good thing.
If the writer is never surprised, the reader cannot be either.