Archie ducked under another beam. Loose dirt sprinkled from the tunnel’s ceiling, falling on them from overhead like rain. “You must have tampered with her car before everyone else showed up,” he said.

“Even an old Saab has a computer,” Gretchen said, brushing the dirt from her shoulders. “I hacked the electronic control system of her car, and then I was able to control the car’s computer wirelessly from a laptop.” She touched his elbow. “Watch this rock,” she said, shining the lantern in front of him, to illuminate a rock in his path the size of a lunchbox. Archie stepped around it.

“The car’s computer controls the radio,” Gretchen continued. “The horn. The engine. It’s really quite amazing. Susan doesn’t vary her route from your house, you know. I didn’t even have to follow her. I went ahead, and waited. And then I offered her a ride.” She smiled. “I think I might have frightened her.”

Another rat darted from the light. The ceiling spit more dirt in Archie’s hair. “So you drove her somewhere,” Archie said. He was trying to puzzle out what time Susan had left his apartment, how far Gretchen could have gotten with her in order to make it back to his house when she did. He thought that Susan had left between ten and ten-thirty. Gretchen had shown up just past one A.M.

“I’ll save you the math, darling,” Gretchen said. “I had almost three hours to take her somewhere and get back to you,” she said. “And I’ll give you a hint, I didn’t drug her.”

“You needed her mobile,” Archie said. He searched the tunnel floor ahead of them for signs of footprints. Gretchen had been down here before—maybe Susan had been her first guest. But the uneven ground threw too many shadows for Archie to make out any trace of disturbed ground.

“No one comes down here anymore,” Gretchen said idly. “Jack and his people don’t use these parts of the tunnels.”

“I wonder why,” Archie said.

Archie ducked under another timber support beam that had disintegrated to cobwebs and splinters, and tried not to think about the ten thousand pounds of pressure from the lake pressing to get in.

They kept going, advancing in silence, Archie’s mind busy trying to figure out if Susan was really somewhere down there, or if Gretchen just wanted him to think that Susan was down there somewhere so that he’d trudge along obediently beside her. Occasionally he glanced around at the darkness that filled in behind them. It was complete black, like the world was evaporating with each of their steps, disintegrating into nothingness. Archie remained close to Gretchen. He didn’t want to risk stepping outside of the light.

“I have a surprise for you,” Gretchen said.

Gretchen’s surprises were never good. “Will it use up my health insurance deductible?” Archie asked.