Nothing in a forest grows in a straight line. Roots wander. Paths bend. Trees fall where they like.
So when a line of fire appears across open ground, evenly spaced and holding rank, you know something made it.
That's the Sheriff. He doesn't search and he doesn't hunt. He rides one full row and one full column, and everything he crosses is taken. Nine glades out of twenty five.
You don't find out which nine until he's already through.