Lawrence was already moving. He'd pulled out his wand and was casting the detection charm on the exposed rock before Rowan or Iris had taken more than a few steps toward the structure. Iris ran the same charm from a different angle and looked at her parchment.
"The resonance here is ten times what we measured on the ridge last week," she said.
Lawrence didn't respond. He was working the ground around the structure systematically, checking exposed rock faces, splitting likely stones with his wand, examining each one. Rowan and Iris spread out and did the same, covering the valley floor in a grid pattern while the wind blew over the ridgeline above them.
Lawrence found it forty minutes in.
"Here." His voice was flat and controlled in the way it got when he was suppressing something large. He was kneeling beside a fissure in the rock at the base of the eastern wall, where a crack in the stone had allowed water to seep and mineral deposits to accumulate over centuries. In the crack, crusted with feldspar and mica, was a vein of something that caught the light differently from the surrounding rock. Translucent, milky-blue, with an internal shimmer that shifted as Rowan moved his wand over it.
Moonstone. Ritual grade. Two inches of it visible in the crack and likely more beneath.
Lawrence sat back on his heels. His hands were shaking. He didn't say anything for a while. He just looked at it.
Then he pulled a chisel from his bag, a thin tool he'd brought for exactly this purpose, and started working the moonstone free from the surrounding rock. His hands steadied as soon as he started the work. The shaking stopped. Iris held a light over the fissure while Lawrence carved, precise and careful, and Rowan watched the structure.
He didn't go inside. The entrance was dark and the magic radiating from the interior was dense enough that his diagnostic charms couldn't penetrate it, returning only noise. The walls were unmarked on the outside, no runes, no carvings, nothing to indicate purpose or origin. Just black stone, perfectly fitted, enduring.
The caves below had runes he could partially read. This structure had nothing. As though whoever built it hadn't needed to write anything down.
He copied the cave runes into his journal while Lawrence worked. Something for Fenwick. Or for the library, if Fenwick didn't have answers.
Lawrence worked the moonstone free in three pieces. Each one was wrapped in cloth and placed in his bag with the care of someone handling something irreplaceable. When he finished, he sat on the ground beside the fissure and pressed his palms flat on his knees and looked at the sky.
"Thank you," he said. He wasn't talking to anyone in particular.
Iris put her hand on his shoulder. She left it there for a while and didn't say anything.
They started back down. The return was easier, the route mapped, the thornback territory avoided. They collected Edmund and Poppy at the treeline and found them sitting on a fallen log surrounded by spread parchment and specimen jars. Poppy's notes covered six sheets. Edmund was holding a jar containing something that looked like a strand of silk suspended in clear liquid, and he looked slightly ill.
"The colony is in deep mourning," Poppy reported as they walked. "Every tunnel entrance I found was sealed with fresh silk. The clicking has stopped completely. I think they're down to about fifteen individuals, maybe fewer. Without a queen candidate, they'll start dispersing within the month."
"Good," Lawrence said.
"Good for us. Terrible for the colony." Poppy held up one of her sketch sheets, which showed a cross-section diagram of a thornback tunnel network. "The web architecture is extraordinary. The structural silk they use underground has a tensile strength higher than anything I've read about. I've never seen field data like this."
Edmund looked at the specimen jar he was carrying and then at Poppy. "Can I put this down now?"
"Careful with it. That sample took me an hour to extract."
They walked back through the forest as the light faded. Lawrence was quiet but the silence had a different quality than it had carried all term. Lighter. Something had changed in the set of his shoulders.
The castle appeared through the trees as the sun set. Warm light in the windows. Smoke from the kitchens. Rowan looked at it and thought about the runes in the caves, the structure in the valley, and the dark archway he hadn't gone through.
They went in through the third-floor passage, cleaned up, went to supper, and nobody asked where they'd been.