Alma 62:20

And when the night came, Moroni went forth in the darkness of the night, and came upon the top of the wall to spy out in what part of the city the Lamanites did camp with their army.

When night came, Moroni went out in the darkness of the night. He climbed on top of the wall to see where the Lamanites had set up their camp.

When night fell, Moroni slipped out in the darkness and climbed to the top of the city wall to scout out where the Lamanite army was camped.