But she wasn’t anywhere near the end of the process, as she saw when she scrolled down to the next screen full of formulas and text. Mary’s jaw dropped as she continued to read, discovering what step 4 was. Jock and many members of his team had come from RAND; Mary had gotten used to them speaking in cold-war clichés, but the next term stopped her heart for a second: “Payload delivery.”

If, and only if, the test subject was found to be a Neanderthal, a new cascade sequence was invoked that ultimately resulted in…

Mary could hardly believe her eyes. Her specialty was ancient DNA—that’s what had gotten her involved in all this to begin with, after all—but that didn’t mean she was ignorant of more recently identified sequences, especially those that had made front-page news around the world.

If the specimen was a Neanderthal, a payload was indeed delivered: a payload based on a filovirus that would result very rapidly in the development of a hemorrhagic fever.

A fatal hemorrhagic fever…

Mary leaned back in Jock’s chair. She could taste bile climbing her throat.

Why on Earth would someone want to wipe out the Neanderthals?

But, of course, the question really should be, Why, with two Earths, would someone want to wipe out the Neanderthals?

Hemorrhagic fevers were contagious. Gliksins couldn’t cure them, and she very much doubted Barasts could, either, for two reasons. First, by virtue of never having developed agriculture and animal husbandry, the Neanderthals had also never had to develop techniques for dealing with plagues. And, second, all known hemorrhagic fevers were tropical diseases—something the northern-living Neanderthals would have had very little experience with.

Mary swallowed hard, trying to force down the biting, sour taste.

But why? Why would someone want to kill the Neanderthals? It didn’t make…

Suddenly Mary remembered her little exchange with Jock back at the Debral nickel mine:

“It’s astonishing,” Jock had said. “I knew in an intellectual sort of way that we’d screwed up our environment, but until I saw all this… ” He’d indicated the pristine countryside. “It’s like finding Eden. ”

And Mary had laughed. “Isn’t it, though? ” she’d said. “Too bad it’s already occupied, eh? ”

A little joke—that’s all it was. But Jock hadn’t laughed. All you had to do was get rid of those pesky Neanderthals, and an Eden awaited…

It was horrific—but Jock had spent his life dealing with scenarios of mass destruction. What was horrific to Mary was just another day at the office for him.

Mary’s first thought was to erase the computer files—but, of course, that would accomplish nothing. There would doubtless be backups.

Her second thought was to pick up the phone and call—well, as a good Canadian, she naturally thought of the CBC, which could then spread the news to the four corners of this world. There was no way people would stand for this sort of genocide.

But she didn’t know how far along Jock was. If he was ready to go, Mary certainly didn’t want him to feel cornered, since he might release his disease vector as soon as he heard that the public had gotten wind of his plan.

Mary needed help, ideas, support—not just from Ponter or Adikor, but from another Gliksin, someone who understood how this world worked.

There were people she trusted back in Toronto, but was there anyone she could rely on here in the United States? Her sister Christine—the real Christine—of course, but she was in Sacramento, clear across the continent, thousands of—of miles —away.

And then it hit her.

The obvious answer, as much as her youth and beauty rankled Mary.

The woman who had saved Ponter Boddit’s life when he’d first arrived in this reality.

The quantum-physics postdoc that Jock had scooped up to try to replicate the Neanderthal computing technology.

Louise Benoît.

Not that Louise would be much help in medical matters, but—

But her boyfriend! Granted, Reuben Montego was no specialist, but he’d be a lot more help dealing with a disease vector than would a physicist.

Mary knew that she might never again get access to these computer files. She looked around Jock’s office and found a spindle of blank CDs (Kodak brand, of course, this being Rochester). She took one, put it in the computer’s CD drive, and clicked on the CD-burning application. Just to be on the safe side, she selected all the files in the folder. The whole thing topped out at 610 meg—small enough to fit on a single CD. She clicked the “copy files” button, and leaned back in the Aeron chair—which, just now, didn’t seem comfortable at all—wishing she knew some way to calm her racing heart.

Ponter and Adikor had ended up spending the whole night at the hospital with Lonwis and Jock. Mary had eventually gone home alone to Bristol Harbour Village, without having had a chance to tell Ponter what she’d discovered.

Exhausted, she didn’t get in to Seabreeze until 11:00A.M. , but Ponter, Adikor, and Jock still hadn’t come in yet. After getting an update from Mrs. Wallace on Lonwis’s condition—stable—she climbed the stairs to Louise Benoît’s lab. “How about some lunch?” Mary asked.

Louise looked pleasantly surprised. “Sure,” she said. “When?”

“How about right now?” said Mary.

Louise looked at her watch and was clearly surprised by how early it was. But something in Mary’s voice had obviously got her attention. “Bon, ” she said.

“Great,” said Mary. Their coats were on a rack by the mansion’s front door. They put them on and headed outside, into the crisp November day, a few snowflakes blowing around.

There were several restaurants on either side of Culver Road. Many were seasonal—Seabreeze was a summer resort, after all—but some were open year-round. Mary started walking purposefully to the west, and Louise fell in beside her.

“So,” said Louise, “what do you feel like?”

“I was in Jock’s office last night,” said Mary, without preamble, “while he was off at the hospital with Lonwis. He’s had a virus designed to kill Neanderthals.”

Louise’s accented voice was filled with disbelief. “What?”

“I think he’s going to wipe them out—all of them.”

“Why?”

Mary looked over her shoulder, just to be sure they weren’t being followed. “Because the grass is greener on the other side of the fence. Because he wants to claim their version of Earth for our kind of humans.” She kicked some litter out of her way. “Maybe so we can start over without all this.”

Up ahead, on the left side of the road, an amusement park was visible, closed for the winter, its roller coaster a lump of rusty intestines. “What—what should we do?” said Louise. “How do we stop him?”

“I don’t know,” said Mary. “I only stumbled onto the virus design by accident. My network connection went down, and so I went to his office to use his workstation, since he was gone for the day. But he’d left in such a hurry when Lonwis had his heart attack that he hadn’t logged off his account. I copied the virus designs onto a CD, but I think what I’d really like to do is get back into his account again, and modify the master file so that it won’t produce anything deadly. I presume he’s planning to feed those instructions into the codon writer, and then release the virus into the Neanderthal world.”

“What if he’s already made the actual virus?” said Louise.