They were three flights down when they heard the outer door lock disengage again. Though Dani had been expecting the sound, it made her body jump.

“I see light below us,” Sam said.

Dani realized she could see it too. A faint glow from somewhere at the bottom of the stairwell, just bright enough to rim the edges of the stairs up here.

“Lauren, can you run with us?” Dani asked. “Can you hold the rail and run?”

For a second, as they continued downward, the girl didn’t answer. Then she murmured, “Think so.”

“Then run,” Dani said.

At that moment Pierce wrenched open the second door, above them in the stairwell, hard enough to slam it against the tiles in the entry hall. The glow of his flashlight beam, indirect and wild, began sliding over the walls.

“Run,” Dani said again, and Lauren got moving, sprinting downward even as she held on to Dani’s hand. Sam followed as they went, flight after flight, throwing themselves toward the bottom of the shaft.

They saw the light source as soon as they rounded the final landing. Below them lay the square space with the two doors—one on the right, leading into the massive test chamber, the other on the left, leading somewhere they’d never seen; they’d never had the code for it.

That door on the left stood open now.

Wide open, with light shining through from the other side.

From above them came the clatter of Pierce’s footsteps, no more than two or three flights up.

The three of them took the last set of stairs in a few seconds, their momentum carrying them straight to the open door. They turned and stared through it.

Beyond lay a narrow corridor—a tunnel, really: three feet wide, its walls and floor made of poured concrete, the ceiling a metal gridwork held up by steel beams running across it. At the top of one wall, dim white lights were set into the surface, forming a line that stretched away into the distance, straight as a tightrope.

There was no way to tell what the tunnel led to.

“Try it?” Dani asked.

“It’s one more door we can shut,” Sam said.

It would buy them a few seconds, Dani thought. No reason to waste those same seconds deciding. She shoved Lauren through the doorway and followed after her, with Sam at her back. He pushed the door shut behind them, and they ran.

CHAPTER FORTY-SIX

SEPTEMBER 2018

Dryden stood in the doorframe and stared at the place from his nightmare.

The tunnel.

Three feet wide.

Poured concrete walls and floor.

Metal grid ceiling held up by steel beams crossing it from side to side.

There were small light bulbs set high in one of the walls—dark and dormant now, but once upon a time they had shone dimly white.