Cogito Ergo Sum

'The moment that - that thing entered the room, it swooped down on Crouch and - and...'Professor Minerva McGonagall was quite right in her description of what had occurred in the office of the Defence Against the Dark Arts teacher, and her statement of what she saw was an entirely accurate summation of events. What she didn't see was what happened after. Something involving a dementor, a woman, a watch, and a promise.