Once again Bell glanced down the corridor then nodded. “What’s this all about, Lincoln?”

“Could you check out the window? Make sure Mason’s left? Oh, and I’d close that door again.”

Bell did. Then he walked to the window and looked out. “Yeah. He’s headed up the street. Why all this …?” He lifted his hands to complete the thought.

“How well do you know Mason?”

“As good as I know mosta my deputies. Why?”

“Because he murdered Garrett Hanlon’s family.”

“What?” Bell started to smile but the expression faded fast. “Mason?”

“Mason,” Rhyme said.

“But why on earth?”

“Because Henry Davett paid him to.”

“Hold up,” Bell said. “You’re a couple steps past me.”

“I can’t prove it yet. But I’m sure.”

“Henry? What’s his involvement?”

Rhyme said, “It all has to do with the Blackwater Canal.” He fell into his lecturing mode, eyes on the map. “Now, the point of digging the canals in the eighteenth century was having dependable transport because the roads were so bad. But as the roads and railroads got better, shippers stopped using the waterways.”

“Where’d you find all this out?”

“Historical Society in Raleigh. Talked to a charming lady, Julie DeVere. According to her, Blackwater Canal was closed just after the Civil War. Wasn’t used for a hundred thirty years. Until Henry Davett started running barges on it again.”

Bell nodded. “That was about five years ago.”

Rhyme continued, “Let me ask—you ever wonder why Davett started using it?”

The sheriff shook his head. “I remember some of us were a little worried kids’d try to swim out to a barge and get hurt and drown but none of ’em ever did and we never thought any more about it. But now you mention it I don’t know why he’d use the canal. He’s got trucks coming and going all the time. Norfolk’s nothing to get to by truck.”

Rhyme nodded up at the evidence chart. “The answer’s right up there. That one bit of trace I never did find a source for: camphene.”

“The stuff in the lanterns?”

Rhyme shook his head, grimaced. “No. I made a mistake there. True, camphene was used in lanterns. But it’s also used in something else. It can be processed to make toxaphene.”

“What’s that?”