Not without warning—always the growl behind them or ahead. When crystal veins in the rock took fire, they ran or hid. Once, they could not run. Tara knelt in the tunnel’s center, Crafted a ward, and held Shale close as the fire buckled her shield. If the mind that moved this mountain wanted to crush them, it would.

“Are you certain there’s a mind?” Shale asked.

“I hope there isn’t, so I’ll assume there is.”

They descended for hours. Back on the mythical surface, the Alt Coulumb express winged east. Tunnels turned back on themselves, confounding Tara’s stubbornly two-dimensional map. She could see Craftwork woven through the stone, which would help her retrace her steps; finding a way down was harder.

She thought she recognized a triple junction through which they passed. Were they lost? She carved a glyph into the stone above the center passage. When they reached the triple junction again, the glyph was gone. Either she’d been wrong, or the something erased the glyph.

Cave air tasted close and dank.

She had to sleep, after a while. “That or collapse.” One side chamber, hewn to store drill bits and spare equipment, had walls free of crystal, which she hoped meant they’d be safe from the lightning here.

Shale kept first watch. Tara unfolded a sleeping pad from her pack. She hung her jacket on a lantern hook, made a pillow of her knapsack, and slept in a cave silence broken only by Shale’s breathing.

Nightmares struck, as hoped: a message from Wakefield, reporting the Alt Coulumb team was ready to defend Kos. Next she saw Abelard, praying alone in an enormous chapel; the altar grew, and the chapel’s flames melted his flesh from his bones. She did not know if Abelard sent her that dream, or if she built it for herself. After that, the bad dreams were real.

A hand on her shoulder woke Tara to the tunnel’s black. She recoiled from the touch, scraped her knuckles against the wall, cursed, and summoned a light. Shale crouched beside her. “We should go.”

“You kept watch without lights?”

“I thought we should save the hand torches,” he said. “I hear well.”

She smoothed the wrinkles in her suit and adjusted her slept-on hair. A small rodent had crawled into her mouth, died, and rotted. She swished canteen water in her mouth, gargled, and spit in the corner. Checked her watch again—the dawn flight had left already. “Any more lightning?”

“Five clusters passed.”

They returned to the tunnels and the blunt smell of undisturbed stone.

“Do you think the lightning-balls are guards?” Shale asked.

“Bad ones, if so. We’re not dead yet.”

“They’d have killed us already if not for you.”

“And the first would have got me if not for you. Good thing we keep each other around.”

“Glad to hear I’m a useful asset.”