But it is one thing to trust that instinct about a stranger at a checkpoint and another thing entirely to trust it about the man who is making your grieving mother laugh again for the first time in years.

I did not want it to be true.

And wanting something not to be true is, I have learned, the single most effective way there is to blind a person who is otherwise very hard to blind.

Chapter 4 — The Subtle Turn

The change in Gavin began almost the moment the wedding was over, and it began so gradually, so reasonably, that I understand completely how my mother failed to see it happening.

That is how this particular kind of harm works.