This is just a perfect chance.
___
Corvo: Lands on the roof, and pulls out his blade, it shines under the moonlight and is quickly afterwards sheathed. The man silently jumps down in the bushes, and walks out from behind seeing a few suspicious guards. He approaches them, and in a second takes them out, he drags their lifeless bodies behind the bushes, unseen even by the moon. Corvo walks inside the Ball.