It was, our lawyer explained, as ironclad a document as such a thing can be: she could never again make a legal claim on our daughter, never register her to any trust, never send another investigator, never appear in another doorway.

The mark that Wendy had spent five years hunting for, the crescent behind our daughter’s ear that was supposed to bind Fiona to that dark family forever, had instead become the occasion for severing the connection permanently, because in coming to claim the child, Wendy had forced the confrontation that ended her hold on all of us.

She had reached for leverage and found, instead, the one man no longer afraid of her, holding five years of her secrets.

There is a lesson in that reversal that I have savored quietly ever since, because it is a lesson about the limits of a certain kind of power.