Mary let Ponter lead the way out onto the metal deck that formed a roof over the ten-story-tall barrel-shaped cavern that used to house the Sudbury Neutrino Observatory. Instead of having to descend through a hatch just a meter on a side, as she’d done the last time she was here, a large opening had been carved into the decking, and an elevator had been installed—Ponter remarked that it was new since his latest arrival. The elevator had acrylic see-through walls; they’d been made especially for this site by Polycast, the company that had manufactured the acrylic panels of which the now-dismantled heavy-water containment sphere had been composed.

The elevator was the first of many modifications planned for this chamber. If the portal really did stay open for years, the chamber would be filled in with ten stories of facilities, including customs offices, hospital rooms, and even a few hotel suites. Currently, though, the elevator had only two stops: the chamber’s rocky floor, and, three stories above that, the staging area that had been built up around the portal. Ponter and Mary got off at the staging area, a wide wooden platform with yet another couple of soldiers stationed on it. Along one side of the platform were the flags of the United Nations and the three countries that had jointly funded SNO: Canada, the United States, and Great Britain.

And, in front of her, was—

It indeed seemed to have acquired the popular name of “the portal,” but because of the Derkers tube protruding through it, it looked more like a tunnel. Mary’s heart was pounding; she could see through it—see the Neanderthal world, and—

My God, thought Mary. My God.

A brawny figure had passed by the far end of the tunnel, someone working on the other side.

Another Neanderthal.

Mary had seen much of Ponter and some of Tukana. Still, she had trouble really accepting that there were millions of other Neanderthals, but…

But there was another one, down the tunnel.

She took a deep breath, and, since Ponter was gallantly indicating she should go first, Mary Vaughan, citizen of one Earth, started walking down the cylindrical bridge that led to another Earth.

A flat insert had been crafted for the bottom of the Derkers tube, making a smooth walkway. Mary could see the blue ring surrounding the tube, visible through its translucent white walls: the actual portal, the opening, the discontinuity.

She reached the threshold of that discontinuity, and stopped. Yes, Ponter had gone through in both directions now, and, yes, a number of Homo sapiens had preceded her in crossing over, but…

Mary broke into a sweat, and not just because of the subterranean heat.

Ponter’s hand landed on her shoulder. For one horrible second, Mary thought he was going to push her through.

But of course he didn’t. “Take your time,” he whispered, in English. “Go when you are comfortable.”

Mary nodded. She took a deep breath and stepped forward.

It felt like a ring of ants crawling over her body from front to back as she stepped across the threshold. She’d started with a slow step, but quickly hopped forward to put an end to the unsettling sensation.

And there she was—centimeters, and tens of thousands of years of divergence, from the world she knew.

She continued down to the end of the tunnel, Ponter’s footfalls heavy behind her. And then she stepped out, into what she knew must be the quantum-computing chamber. Unlike the SNO cavity, which had been co-opted from its original purpose, Ponter’s quantum computer was still fully operational; indeed, Mary was given to understand that without it, the portal would slam shut.

Four Neanderthals stood in front of her, all male. One was wearing a garish silver outfit; the others were wearing sleeveless shirts and the same strange pants with boots attached that Ponter had arrived in. All of them, like Ponter, had their light-colored hair parted precisely in the center; all were hugely muscled, with short limbs; all had undulating browridges; all had massive, potato-like noses.

Ponter’s voice came from behind her, speaking in the Neanderthal language. Mary swung around in surprise. She heard Ponter whisper that language all the time, with Hak translating the words into English at a much-louder volume, but, till now, she’d never heard Ponter speak loudly and clearly in his native tongue. Whatever he’d said must have been a joke of some kind, as all four of the Neanderthals emitted deep, barking laughs.

Mary stepped away from the mouth of the tunnel, letting Ponter pass. And then—

She’d heard Ponter talk frequently about Adikor, of course, and had understood intellectually that Ponter had a male lover, but…

But, despite her liberal leanings, despite all her mental preparations, despite the gay men she knew back on her Earth, she felt her stomach clench as Ponter embraced the Neanderthal who must be Adikor. They hugged long and hard, and Ponter’s broad face pressed against Adikor’s hairy cheek.

Mary realized in an instant what she was feeling, but, God, it had been decades since she’d experienced that particular emotion, and it shamed her. She wasn’t repulsed by the display of same-sex affection; not at all—hell, you couldn’t flip channels on Toronto TV on a Friday night without running into some gay porn. No, she was…

It was shameful, and she knew she’d have to get over it fast if she was ever to have a long-term relationship with Ponter.

She was jealous.

Ponter let Adikor go, then he held up his left arm, facing its inside toward Adikor. Adikor raised his arm in a matching gesture, and Mary saw symbols flash across the displays on each man’s Companion implant; Ponter was presumably receiving his accumulated messages from Adikor, to whom they had been forwarded in his absence.

They lowered their arms at the same time, but Ponter only brought his halfway down, and he pivoted his forearm at the elbow to indicate Mary. “Prisap tah Mare Vonnnn daballita sohl,” he said, but, since he wasn’t addressing her, Hak provided no translation.

Adikor stepped forward, smiling. He had a kind face, broader than Ponter’s—indeed, as broad as a dinner plate. And his round deep-set eyes were an astonishing teal color. The overall effect was a Flintstones version of the Pillsbury Doughboy.

Ponter’s voice dropped to a whisper, and Hak’s voice provided a normal-volume translation. “Mare, this is my man-mate, Scholar Adikor Huld.”

“Hollow,” said Adikor. Mary was baffled for a moment, then realized that Adikor was trying to say “hello,” but hadn’t quite gotten the vowel sounds right. Still, she was impressed, and touched, that he’d tried to learn some English.

“Hello,” said Mary. “I’ve heard a lot about you.”

Adikor tipped his head, presumably listening to a translation through his own Companion’s cochlear implants, and then, in a startlingly normal response, he smiled, and, in his accented English, said, “All good, I hope.”

Mary couldn’t help but laugh. “Oh, yes,” she said.

“And this,” said Hak’s voice, speaking for Ponter, “is an Exhibitionist.”

Mary was taken aback. Ponter was referring to the guy dressed all in silver. She wasn’t quite sure what she’d do if this strange Neanderthal whipped it out in front of her. “Umm, pleased to meet you,” she said.

The stranger didn’t have the trick down of whispering his own words while his Companion translated loudly. Mary had to struggle to separate the Neanderthal noise from the English. “I have learned,” she picked out, “that in your world, I might be called a reporter. I go to interesting places, and let people tune into what my Companion is broadcasting.”

“All Exhibitionists wear silver,” said Ponter, “and nobody else does. If you see someone dressed this way, be warned that many thousands of people are watching you.”