Knife edge

“Thank you, Flannery,” Anne said, her low voice a knife edge between sincerity and sarcasm, “for saving my life."

While I'd never been to Pakistan, I'd seen plenty of towns like this one just across the border in Afghanistan, perched on a knife edge between life and death, settlements where the people had nothing in their lives except for war, a few goats and a lot of religion.

I'm on a knife edge, Lydia, don't you see?