“That’s how it works,” she said. “You keep moving the vial until the dog learns to find the scent source and not the cinder block. Then you start hiding the vial in other places: in the woods, hanging from a tree, buried underground. You keep making it more and more difficult and you use the scent in lower and lower concentrations until the dog can find it anywhere—if he has the gift.”

“How long does the training take?”

“It depends on the dog. These pups are really too young to train. I usually wait until they’re about a year—before that they’re adolescents and they have a hard time paying attention. They just want to play.”

“Say no more.”

“That’s basically all there is to it.”

“I have a feeling there’s a lot more to it than that.”

“There’s time—days and weeks and months and years. The training never stops.”

“Even for your three-legged dog—the one you call ‘Trygg’?”

“Who told you her name?”

“Gunner.”

“You talked to him again?”

“This morning, before I came up here.”

She frowned. “What did he tell you this time?”

“He told me about your father and the Canine Enforcement Training Center in Front Royal. He told me that your father disappeared one day and that you’ve lived up here by yourself ever since—that you basically raised yourself. He also told me why you hate the people down in Endor, and I can’t say I blame you.”

“Gunner’s got a big mouth,” she grumbled.

“He told me that he and Rose love you like a daughter, and it’s pretty clear that they do. He also said that I put you in danger, and that makes me responsible for your safety.”

“You don’t owe me anything.”

“I owe you a lot—so does the FBI. We couldn’t have found those graves without you.”

Alena shook her head. “You didn’t come up here just to learn about cadaver dogs, did you?”

“No. I thought if I spent a little time with you, you might trust me more.”

“Why does that matter?”

“Because I might need your help again.”

She didn’t respond.

“Look, Marge still hasn’t come back. I told the police about her this morning; they picked up her dog and they’re beginning a search. I think Marge is dead, and I think the guy who killed her is connected to the Patriot Center murders—but we have to find him using twenty- to fifty-year-old bones, and that’s very hard to do. If it’s the same killer, then Marge might be our best way of finding him—but we have to find Marge first. That’s why we need you.”

“I don’t want to get more involved,” Alena said.