“I’m supposed to be learning here.” He took out a second plastic bag containing a short length of PVC pipe. “What’s this one?”

“Submerged remains.”

“That’s interesting. When a body decomposes in a wet environment it forms a waxy substance called adipocere—that must be what the dog is detecting.” He held the bag up to Alena. “Do you mind?”

“Knock yourself out—if you’re not careful, you will.”

Nick opened the bag and sniffed. “It smells just like the other one. I can’t tell the difference.”

“That’s because you only have about five million olfactory cells in your nose; a dog can have two hundred million—one-eighth of its brain is dedicated to smell. Dogs have an incredible ability to distinguish scents. You walk into a kitchen and smell beef stew; a dog walks into a kitchen and smells beef, carrots, peas, potatoes—it’s called ‘odor layering.’ He can even smell the salt—even in a dilution of one in ten million.”

“Question,” Nick said. “If a dog’s sense of smell is so much more sensitive than a man’s, how come a dog will stick its nose in your crotch?”

She squinted at him. “Are you always like this?”

“What? That was a good question.”

She set the scent vial down on the ground and placed one of the puppies in front of it. The dog sniffed at the vial once, then cowered and backed away.

“See what he’s doing? A lot of dogs are instinctively repulsed by the smell of death. He’s out—he’ll never make a cadaver dog.”

“Just like that? No second chances?”

“It isn’t something he can learn. He was either born with it or he wasn’t—and he wasn’t. It’s not his gift.” She picked up the dog and looked into its eyes. “No—he doesn’t have it in him. I should have seen it before.”

“Wait a minute,” Nick said. He picked up a second dog and handed it to her. “Try this one—but look at it first and tell me what you think it’ll do.”

She took the dog and looked into its eyes. “This one’s all play and no work—he’ll have the opposite problem.” She set the dog in front of the vial and watched; the dog took the vial in its mouth and began to run off. She reached down and lifted it by the scruff of its neck. “Some dogs love the scent of death—they’re no good either. You’re looking for a dog that doesn’t care—a dog that will treat it just like any other smell.”

She tested three more puppies; the third one sniffed at the vial and made no response at all. Alena looked at its face. “He might make it, he might not.”