In a deserted side-road of Diagon Alley, where scraps of un-Vanished trash could be seen lodged into the edges of the brick street and the blank brick building-sides that surrounded it, along with scattered dirt and other signs of neglect, an ancient wizard and his phoenix Apparated into existence.

The wizard was already reaching within his robes for his hourglass when, in habit, his eyes jumped to a random spot between the road and the wall, to memorize it -

And the old wizard blinked in surprise; there was a scrap of parchment in that spot.

A frown crossed Albus Dumbledore's face as he took a step forward and took the crumpled scrap, unfolding it.

On it was the single word "NO", and nothing more.

Slowly the wizard let it flutter from his fingers. Absently he reached down to the pavement, and picked up the nearest scrap of parchment, which looked remarkably similar to the one he had just taken; he touched it with his wand, and a moment later it was inscribed with the same word "NO", in the same handwriting, which was his own.

The old wizard had planned to go back three hours to when Harry Potter first arrived in Diagon Alley. He had already watched, upon his instruments, the boy leaving Hogwarts, and that could not be undone (his one attempt to fool his own instruments, and so control Time without altering its appearance to himself, had ended in sufficient disaster to convince him to never again try such trickery). He had hoped to retrieve the boy at the first possible moment after his arrival, and take him to another safe location, if not Hogwarts (for his instruments had not shown the boy's return). But now -

"A paradox if I retrieve him immediately after he arrives in Diagon Alley?" murmured the old wizard to himself. "Perhaps they did not set in motion their plan to rob Azkaban, until after they had confirmed his arrival here... or else... perhaps..."