[Boone's gaze turns towards the trees again, suspicious. Is that how Rex feels too?]

If you go past the fence? Or too close to the trees?

[If it's the trees, then maybe whatever's out there just wised up and stopped moving after all. Or maybe they moved further back, where the trees would hide all movement. Either way, Boone doesn't like it. He lifts his rifle and looks through his scope again, just incase.]