He followed the sound of her voice. What he thought was a sheer drop was actually a rocky decline, steep but passable. Amy was already moving down the twisting path. He took a breath of icy air, willing his fear away, and followed.

The path grew narrower, running horizontally to the mountain’s face as it descended, clinging to it like a catwalk. To his left, sheer rock, glinting with moonlit ice; to his right, an abyss of blackness, a plunge into nothing. Even to look at it was to be swept away; he kept his eyes forward. The women were moving quickly, shadowy presences leaping at the far edge of his vision. Where was Lacey taking them? What was the weapon she had spoken of? He could hear the voice of the river again, far below. The stars shone hard and pure above his face, like chips of ice.

He turned a corner and stopped; Lacey and Amy were standing before a wide, pipelike opening in the mountain’s face. The hole was as tall as he was, its depthless interior a maw of blackness.

“This way,” said Lacey.

Two steps, three steps, four; the darkness enveloped him. Lacey was taking them inside the mountain. He remembered the tin of matches in his coat. He stopped and struck one, his insensate fingers fumbling in the cold, but as soon as it sparked, the swirling currents of air puffed the flame away.

Lacey’s voice, from up ahead: “Hurry, Peter.”

He inched his way forward, each step an act of faith. Then he felt a hand on his arm, a firm pressure. Amy.

“Stop.”

He couldn’t see anything at all. Despite the cold he had begun to sweat under his parka. Where was Lacey? He had spun around, searching for the opening to orient himself, when from behind him came a squeal of metal, and the sound of an opening door.

Everything blazed with light.

They were in a long hallway, carved from the mountain. The walls were lined with pipes and metal conduits. Lacey was standing at a breaker panel on the wall adjacent to the entrance. The room was illuminated by a bank of buzzing fluorescent lights, high above.

“There’s power?”

“Batteries. The doctor showed me how.”

“No batteries could last this long.”

“These are … different.”

Lacey swung the heavy door closed behind them.

“He called it Level Five. I will show you. Please come.”

The hallway led to a wider space, sunk in darkness. Lacey moved along the wall to find the switch. Through the soles of his wet boots he could feel a kind of humming, distinctly mechanical.

The lights buzzed and flickered to life.