The Tenth Circle Read online

Trixie remembered learning that the human body was, like, sixty percent water. How many degrees below zero did it have to get before you literally froze to death?

  “Come on,” Willie said. “Let’s get some grass.”

  The last thing Trixie wanted to do right now was smoke weed. She tried to shake her head, but even that set of muscles had stopped working. When she didn’t get up, he turned away, as if she wasn’t even worth bothering with. “Wait,” she said, and although he didn’t look at her, he stopped moving. She wanted to explain how her feet felt like blocks and her fingers stung so bad that she had to keep biting down on her lower lip. She wanted to tell him how her shoulders hurt from trying not to shiver. She wanted to tell him she was scared and that when she imagined running away, this hadn’t entered into it. “I c-can’t move,” Trixie said.

  Willie knelt beside her. “What can’t you feel?”

  She didn’t know how to answer that. Comfort? Safety?

  He began unlacing Trixie’s boots. Matter-of-factly, he cupped his hands around one of her feet. “I don’t have a sleeping bag. I let my cousin Ernie take it, he’s one of the mushers, and the officials check to see if you have one before you start the race.” Then, just when Trixie could move her toes again, just as a searing burn shot from her nails to the arch of her foot, Willie stood up and left.

  He came back a few minutes later with an armful of dead grass.

  It was still dusted with snow; Willie had dug it out from the edge of the riverbank. He packed the grass in Trixie’s boots and mittens. He told her to stuff some under her parka.

  “How long will it snow?” Trixie asked.

  Willie shrugged.

  “How come you don’t talk?”

  Willie rocked back on his heels, his boots crunching in the snow. “How come you think you have to talk to say something?” He pulled off his mittens and toasted his hands over the fire. “You’ve got frostnip.”

  “What’s that?”

  “Frostbite, before it happens.”

  Trixie tried to remember what she knew about frostbite. Didn’t the affected body part turn black and fall off? “Where?” she panicked.

  “Between your eyes. On your cheek.”

  Her face was going to fall off?

  Willie gestured, almost delicately, in a way that let her know he wanted to move closer to her, to place his hand on her. It was at that moment that Trixie realized she was in the company of a boy who was stronger than she was, in the middle of nowhere, a good twenty-five miles away from anyone who’d hear her scream. She leaned away from him, shaking her head, as her throat closed like a rose after dark.

  His fingers caught her at the wrist, and Trixie’s heart started hammering harder. She closed her eyes, expecting the worst, thinking that maybe if you’d lived a nightmare once it wasn’t quite as bad the second time around.

  Willie’s palm, hot as a stone in the sun, pressed against her cheek. She felt his other hand touch her forehead, then sweep down the side of her face to cup her jaw.

  She could feel calluses on his skin, and she wondered where they’d come from. Trixie opened her eyes and, for the first time since she’d met him, found Willie Moses looking right at her.

  Skipper Johanssen, the mitochondrial DNA expert, was a woman. Bartholemew watched her pour sugar into her coffee and look over the notes on the case that he’d brought. “Unusual name,” he said.

  “Mom had a Barbie thing going on.”

  She was beautiful: straight platinum hair that swept the middle of her back, green eyes hidden behind her thick-framed black glasses. When she read, sometimes her mouth formed the words. “What do you know about mitochondrial DNA?” she asked.

  “That you can hopefully use it to compare two hairs?”

  “Well, yeah, you can. The real question is what you want to do with that comparison.” Skipper leaned back in her chair. “Thanks to C.S.I., everyone’s heard about DNA analysis. Most of the time they’re talking about nuclear DNA, the kind that comes, in equal halves, from your mother and your father. But there’s another kind of DNA that’s the up-and-comer in the forensic community-mitochondrial DNA. And even though you may not know a lot about it, you-and the rest of the world-know the largest case in history where it was used: 9/11.”

  “To identify the remains?”

  “Exactly,” Skipper said. “Traditional efforts didn’t work-they couldn’t find intact teeth, or bones that weren’t crushed, or even anything to X-ray. But mtDNA can be used to profile samples that have been burned, pulverized, you name it. All scientists need is a saliva sample from a family member of the deceased in order to make a comparison.”

  She picked up the hair sample that Max had scrutinized under a microscope the previous day. “The reason we can test this for DNA-without a root attached-is that a cell isn’t made up of just a nucleus. There are many more parts-including the mitochondria, which are basically the powerhouses that keep the cell functional. There are hundreds of mitochondria in a cell, as compared to a single nucleus. And each mitochondrion contains several copies of the mtDNA we’re interested in.”

  “If there’s so much more mtDNA than nuclear DNA, why isn’t it used all the time for criminal profiling?” Bartholemew asked.

  “Well, there’s a catch. Typically, when you get a nuclear DNA profile, the chances of finding another person with that profile are one in six billion. Mitochondrial DNA stats are far less discriminating, because unlike nuclear DNA, you inherit mtDNA only from your mom. That means that you and your brothers and sisters all have the same mtDNA she does…and that her mom and siblings do, and so on. It’s actually fascinating-a female egg cell possesses tons of mitochondria, as compared to the sperm cell. At fertilization, not only are the few sperm mitochondria totally outnumbered, they’re actually destroyed.” Skipper smiled brightly. “Natural selection at its finest.”

  “It’s a pity you have to keep us around for that whole fertilization thing in the first place,” Bartholemew said dryly.

  “Ah, but you should see what’s going on next door to me in the cloning lab,” Skipper replied. “Anyway, my point is that mtDNA isn’t helpful if you’re choosing between two biological siblings to pinpoint a suspect, but it’s a nice tool if you’re looking to exclude someone nonrelated from an investigation. Statistically, if you test fifteen spots on the DNA strand, there are more than an octillion nuclear DNA profiles, which is awfully nice when you’re in front of a jury and trying to pin down a particular individual. But with mtDNA, there are only forty-eight hundred sequences logged to date…and another six thousand reported in scientific literature. With mtDNA, you might wind up with a relative frequency of point one four or something like that-basically, a subject will share a profile with four percent of the world’s population. It’s not specific enough to nail a perp without reasonable doubt in front of a jury, but it would allow you to rule someone out as a suspect because he or she doesn’t have that particular profile.”

  “So if the mtDNA profile of the hair found on the victim’s body doesn’t match the one for Trixie Stone’s hair,” Bartholemew said, “then I can’t link her to the murder.”

  “Correct.”

  “And if it does match?”

  Skipper glanced up. “Then you’ve got reasonable cause to arrest her.”

  The sun skipped the Alaskan tundra. At least, that’s how it seemed to Laura, or why else would it be pitch-dark at nine in the morning? She anxiously waited for the flight attendant to open the hatch of the plane, now that they had landed in Bethel. It was bad enough that she had a fear of heights and hated flying, but this was only half a plane, really-the front end was devoted to cargo.

  “How are you doing?” Daniel asked.

  “Fantastic,” Laura said, trying to lighten her voice. “It could have been a Cessna, right?”

  Daniel turned just as they were about to exit the plane and pulled up the hood of her jacket. He tugged on the strings and tied them under her chin, just like he used to do when Trixie was tiny and headed out to play in the snow. “It’s colder than you think,” he said, and he stepped onto the rollaway staircase that led to the runway.

  It was an un