“...and that's-” Aegis Vigil stopped in mid-sentence, looking very disconcerted.

“What is it?” Luna asked, ears moving back in unease.

“I... I don't know.” the golden alicorn shook his head and closer his eyes. “It was as if I was suddenly reminded of something... but I do not know what...”

“How strange.” commented Luna. “Did you leave a lamp burning in the real world too long?”

“No, no.” denied Aegis. “It's more than that. It's... something I should remember, but I don't. It'll come to me later. It's happened a few times in the last years anyway. Now, where was I?”

“You said 'and that's-'” Luna reported.

“Ah. And that's why, Luna, you need to keep a constant watch on your perimeter. It doesn't matter if the pegasi think patrol duties beneath them, being taken by surprise is the last thing you want here...”

Author's Notes:

Ruh roh.

Note: Luna and Aegis are talking in the dreamworld, in case it's not clear.