When I was a teen, my grandfather had alzheimers, a failing heart, and half of one lung. He was covered with scars and sometimes muttered at walls.
I was asked to keep an eye on him, briefly, one afternoon, while my grandmother did something else. While I was alone with him, he looked at an empty space right next to me, and whispered: "Mom? Dad? Is that you?"
With the exception of getting hit by a car, that was the most terrifying moment of my life.
