"Well, it doesn't work exactly like that," Kate laughed. "First of all, it takes a lot of energy, so they don't have the focus generally speaking to be able to hone in on the parts of your life where you really don't want your brother to be watching. They tend to save their energies for the things that are important. And, second, most seers have learned to put up some good boundaries to protect their own energies. If you've ever had a hotel room with a door to make it adjoin to the room next door, it's rather like closing that door for the night. Its blocking that contact off temporarily to give yourself some peace. Angus is entirely too new to know how to do that, but I'll teach him."
"You know what I don't see?" Angus asked.
"No. What?" Marcus asked.
"Footprints. There should be some in the soil here, but there aren't," Angus said. "None at all."
"Well, maybe they know a charm to obliterate them. It wouldn't be that hard," Marcus said. "A bit of a breeze would blow the dirt and dust in here around and erase every trace they'd ever been here."
"And leave us clueless."
"Maybe. What am I smelling?"
"I dunno. What?"
"You need to work on your powers of observation. I smell something. Something chemical."
"Oh. That. That isn't anything. That's just some of the fertilizer we use on the crops," Angus said, Marcus scowled at him.
"As Sherlock Holmes once said, 'You see but you do not observe,'" Marcus said. He flicked his wand to cast a quick spell, and the light from his wand shot off to his left. "See that? Direction spell. The light shows true north. It's pointing left, so we're going east. Actually northeast. Towards the fields. This is the absolute opposite direction of the other tunnel we found some months ago."
"Which means we have to be under the fields. We're smelling fertilizer because they're planting and fertlizing the fields for this years crops."
"So where will we end up when we reach the northeastern corner? What's on the other side of this property boundary?"
"It's just scrub land and an old abandoned quarry. Mostly sandstone and quartz, but most of the rock that was useful to muggles was all mined out a long time ago. Muggles just rip stuff up and then walk away and leave a right mess."
"I bet you a fish and chips supper we come out in that damned quarry," Marcus said. "Quarries run rampant with tunnels. We're gonna end up over there, I bet."
"Could be," Angus said. "This is awfully far below the surface though."
"Well, most protection grids don't even attempt to reach below what would be about 7-10 feet--the depth of a cellar. They could have laid it this deep to avoid our grids," Marcus said.