And, despite Adikor’s suggestion, Mary was sure Jock Krieger never meant for his Wipeout virus to be introduced to this version of Earth. It was doubtless intended for the other version, the Neanderthal world, a serpent for the un-spoiled Eden.

Of course, if everything went as planned, if she managed to stop Jock, no virus would be released in the Neanderthal world.

But if one was to be, well, hopefully it would be Mary’s Surfer Joe, either in the version she’d just produced, which did nothing, or…

Or…

She could make a more radical revision, producing a version that modified the original logic to act only if—

It was simple, so simple.

A version that would act only if the host cell the virus had invaded did not belong to a Neanderthal, and did contain a Y chromosome.

If, and only if…

Mary frowned. A revised Surfer Joe.

A Mark II—just like the new Pope, taking it all one step further.

She shook her head. It was madness. Sinful.

Or was it? She’d be protecting an entire world from male Homo sapiens. After all, if she and the paleoanthropologists who shared her view were right, it had been male Homo sapiens —the hunters in the clan, not the gatherers, not the women—who had slaughtered their browridged cousins here until not a single one was left.

And now, using the tools of the twenty-first century and technology borrowed from the Barasts themselves, male Homo sapiens were preparing to do again what male H. sap had done once before.

Mary looked at Jock’s computer screen.

It would be so simple. So very simple. The logic tree was already in place. She only needed to change the sequences being tested for, and which way the logic branched.

Testing for a Y chromosome was easy enough: just pick a gene from the Human Genome Project database that appeared only on that chromosome. Mary rummaged on Jock’s desk for pen and paper, then wrote out the logic in longhand on a yellow ruled pad:

Mary looked at what she’d written over and over again, but couldn’t find a flaw. There was no point at which the logic could get caught in an infinite loop, and there were not one but two checks to make sure she was really dealing with a Homo sapiens male and not a Homo neanderthalensis one.

Of course, it was all moot—surely Jock would be stopped before he could release his virus. Modifying it now was just a safeguard, in case somehow it made it over to the other side.

Mary shook her head and looked at her watch. It was well after midnight—the start of a new day.

She should just go home now. Jock’s Wipeout virus had been defused; it would do nothing at all, assuming, as Mary fervently hoped, that he hadn’t yet used the codon writer to output the actual viral molecules. Surfer Joe would harm no one. That’s all she’d set out to accomplish, after all.

That’s all that needed to be done.

And yet…

And yet.

No one would have to get hurt. She’d find a way to disseminate the information, to make sure that everyone on this Earth knew that it was unsafe for male Gliksins to travel to the Neanderthal world. The Barast tuned-laser decontamination technology would make sure the Surfer Joe virus never got back across the portal to this world. Male Gliksins—the majority that were decent, and the horrible minority that did so very much harm—would be safe, just as long as they left Ponter’s world the hell alone.

Mary took a deep breath, then let it out slowly.

She folded her hands in her lap, the left still showing the pale indentation on the third finger where her wedding ring had once been.

And Mary Vaughan thought and thought and thought.

And at last she unfolded her hands.

And then, of course, she did the only thing she could do.

Mary Vaughan sat bolt upright in her bed at Bristol Harbour Village, suddenly awake.

When does—what do you call it?—‘Two becoming One’? When does that happen next? That’s what Jock had asked yesterday. Mary had been too upset about Lonwis’s deteriorating condition and Ponter’s impending departure to really think about it then, but it hit her now, forcing her awake: why Jock should care.

While Two were One would be the perfect time to release his virus. It would be far easier to infect at least the local population in Saldak when everyone of both sexes was together in the Center—and, of course, there was more intercity traffic during Two being One than at any other time of the month; the virus would be spread rapidly.

The four-day holiday would begin the day after tomorrow. That meant Jock wouldn’t act until then—meaning Mary had to act before then.

She looked up at the ceiling to see what time it was—but she was here, not there, and there was nothing on her ceiling. She turned to the digital clock on the night table, the red digits glowing: 5:04A.M. Mary fumbled to turn on the table lamp, then picked up her phone and called Louise Benoît’s home number in Rochester.

“Allô? ” said a sleepy voice after six rings.

“Louise, it’s Mary. Look—Two become One the day after tomorrow. I’m sure that’s when Jock is going to release his virus.”

Louise was clearly struggling to consciousness. “Two becoming…”

“Yes, yes! Two becoming One. It’s the only time on the Neanderthal world when there’s high population density in their cities, and a lot of intercity traffic. We have to do something.”

“D’accord, ” said Louise, her voice raw. “Mais quoi? ”

“What you said we should do: go to the media, blow the whistle. But, look, it’ll be safer for both of us if we’re back in Canada before we do that. I’ll be out of here in half an hour, meaning I can pick you up by 6:30A.M. We’ll drive up to Toronto.”

“Bon, ” said Louise. “I’ll be ready.”

Mary clicked off and headed for the bathroom, starting the shower running. Now, if she only knew how to blow the whistle. Of course, she’d been interviewed on TV and radio plenty of times now, and—

She thought of a nice female producer she’d met at CBC Newsworld in 1996, back when the only Neanderthals known were fossils, back when Mary had isolated a DNA sample from the Neanderthal type specimen at the Rheinisches Landesmuseum. CBC on-air personalities probably didn’t have listed phone numbers, but there was no particular reason why a producer wouldn’t. Mary headed back into the bedroom, scooped up the telephone handset, dialed 1-416-555-1212, Toronto directory assistance, and got the number she needed.