“Delbridge Loring. Yes, well, he must know that the Foundation is looking for him. If he’s smart he’ll disappear.”

“He can’t do that,” North said.

Sierra slanted him a considering look. “Why not?”

North set the tuning machine down on the floor of the cavern and studied it for a moment. “Because he’s obsessed with finding something. Maybe the tuning device that was designed for Crocker Rancourt.”

“Or maybe he’s looking for more paranormal weapons,” Sierra suggested. “It’s obvious he found a couple.”

“They’re no good to him unless he finds a tuning crystal he can use.” North let his pack slide off his shoulder. “Somehow he ended up with the one that was made for Griffin Chastain.”

“You’re sure there would have been two tuning machines?”

“Rancourt and my grandfather were equal partners in their lab. I’m sure they would each have had a device they could use to work the weapons. But somehow Rancourt must have ended up with Griffin Chastain’s machine.”

“So Loring is looking for Rancourt’s?”

North thought about it for a minute. Got the ping of knowing. “It fits. He’s found a cache of powerful weapons but he doesn’t dare use them for fear of destroying his own aura. He needs Rancourt’s tuning crystal. I think he attacked my father because he thought Dad had found something important at Swan Antiques, maybe an artifact that could lead him to Rancourt’s crystal. That broken radio could have been mistaken for some sort of tuning device.”

Sierra lowered her pack to the floor and gave him an odd look. “You think you’ve found an angle you can work, don’t you?”

“I know what Loring wants now. Yes, I can work with that.”

“There’s only one reason he would think the other tuning crystal will work on the weapons he found,” Sierra said. “Loring must be convinced he inherited Crocker Rancourt’s psychic signature.”

“A man who is willing to take the risks that Loring is taking is in the grip of an obsession. That’s his vulnerability.”

“Okay, I’m not going to argue with your logic,” Sierra said. She sat down on the floor next to her pack and braced her back against the black glass wall. “In my business I run into obsessive types a lot. They’ll take big risks and spend a lot of money to get what they want. They can also be extremely dangerous.”

North lowered himself to the floor beside her. “You don’t really want to work with clients like that for the rest of your career.”

“There must be a better way to make a living. But so far I haven’t found it.” Sierra looked around. “I wonder why they lined this tunnel with black glass.”

“Glass has some interesting properties when it comes to conducting and controlling paranormal energy. It’s not a liquid and it’s not a true crystal. No telling what Bluestone used this tunnel for, but I wouldn’t be surprised if it had something to do with channeling power, maybe from that quicksilver river.”