Have you been taken in?

My book continues at a snail's pace. I'm in a section I really can't rush because I'm introducing together the villain of the piece to the reader, but my heroine sees him only as her long-time mentor. So the description and dialog here need to imply a lot to the reader without making them think the heroine is excruciatingly dumb because she doesn't notice his evil, manipulative nature.

This struggle of course leads me to self-analysis--which is where nearly all my struggles, whether real or fictional, seem to lead me. I began thinking about people who've pulled the stocking cap down over my mascara and I have to admit there are too many. Well, one is really too many, because we'd all like to be wise students of human nature and spot the bad pennies. But we don't. In a way I think it testifies to basic goodness. Those who are pretty decent folks tend to expect the same of others, so they occasionally get surprised by the dastardly.

I'm asking you, and I'd really like to know, if you've been manipulated by anyone, how, and how did you "escape" their influence?