“No. But hold on. I’ll go into the database.”

Rhyme heard frantic clicking. Cooper was also the fastest keyboarder Rhyme had ever met.

“Okay, here we go … Interesting …”

“I don’t need interesting, Mel. I need facts.”

“It’s a terpene—carbon and hydrogen. Derived from plants. It used to be an ingredient in pesticides but it was banned in the early eighties. Its main use was in the late 1800s. It was used for fuel in lamps. It was state of the art at the time—replaced whale oil. Common as natural gas back then. You’re trying to track down an unsub?”

“He’s not an unknown subject, Mel. He’s extremely known. We just can’t find him. Old lamps? So trace camphene probably means that he’s been hiding out someplace built in the nineteenth century.”

“Likely. But there’s another possibility. Says here that camphene’s only present use is in fragrances.”

“What sort?”

“Perfumes, aftershave and cosmetics mostly.”

Rhyme considered this. “What percentage of a finished fragrance product is camphene?” he asked.

“Trace only. Parts per thousand.”

Rhyme had always told his forensic teams never to be afraid to make bold deductions in analyzing the evidence. Still, he was painfully aware of the short time the two women might have to live and he felt they had only enough resources now to pursue one of these potential leads.

“We’ll have to play the odds on this one,” he announced. “We’ll assume the camphene’s from old lanterns, not fragrances, and act accordingly. Now, listen, Mel, I’m also going to be sending you a photocopy of a key. I need you to trace it.”

“Easy. From a car?”

“I don’t know.”

“House?”

“Don’t know.”

“Recent?”

“No clue.”

Cooper said dubiously, “May be less easy than I thought. But get it to me and I’ll do what I can.”

When they disconnected, Rhyme ordered Ben to photocopy both sides of the key and fax it to Cooper. Then he tried Sachs on the radio. It wasn’t working. He called her on her cell phone.

“’Lo?”

“Sachs, it’s me.”

“What’s wrong with the radio?” she asked.

“There’s no reception.”

“Which way should we go, Rhyme? We’re across the river but we lost the trail. And, frankly”—her voice fell to a whisper—“the natives’re restless. Lucy wants to boil me for dinner.”

“I’ve got the basic analysis done but I don’t know what to do with all the data—I’m waiting for that man from the factory in Blackwater Landing. Henry Davett. He should be here any minute. But listen, Sachs, there’s something else I have to tell you. I found significant trace of ammonia and nitrates on Garrett’s clothes and in the shoe he lost.”

“A bomb?” she asked, her hollow voice revealing her dismay.