Hak bleeped.

“Luciferin,” repeated Mary. “It’s the substance that fireflies use to make their tails glow.”

“Ah,” said Ponter. “Yes, this is a similar catalytic reaction. It is our principal source of indoor illumination.”

Mary nodded to herself. Of course the Neanderthals, adapted for a cold environment, wouldn’t like incandescent bulbs that give off more heat than light. The luciferin/luciferase reaction was almost completely efficient, producing light with hardly any heat.

The elevator continued its ascent, the blue-green illumination making Ponter’s pale skin look oddly silverish and his golden brown irises seem almost yellow. There were ventilation holes in the roof and floor of the cab, creating a bit of a breeze, and Mary hugged herself against the chill.

“Sorry,” said Ponter, noting her actions.

“That’s okay,” said Mary. “I know you like it cold.”

“It is not that,” said Ponter. “Pheromones build up in a closed space like this, and the ride up is a long one. The vents make sure passengers are not overly influenced by each other’s scents.”

Mary shook her head in wonder. She hadn’t even made it out of the mine yet, and she was already overwhelmed by the differences—and she’d known she was heading to another world! Her heart again went out to Ponter, who had originally arrived on her Earth with no warning, but had somehow managed to keep his sanity.

At last the elevator reached the top, and the door opened. Even that, though, happened in an unfamiliar way, with the door, which had appeared seamless, folding out of the way like an accordion.

They were in a square chamber perhaps five meters on a side. Its walls were lime green, and the ceiling was low. Ponter went over to a shelf and brought back a small flat box that seemed to be made of something like blue cardboard. He opened the box and removed a shiny construct of metal and plastic.

“The High Gray Council realizes it has no choice but to let people from your world visit ours,” Ponter said, “but Adikor said they have imposed one condition. You must wear this.” He held up the object, and Mary could see that it was a metal band, with a face on it very much like Hak’s.

“Companions are normally implants,” said Ponter. “But we understand that subjecting a casual visitor to surgery is too much to ask. However, this band is unremovable, except in this facility; that is, the computer within knows its location and will only allow the clasp to reopen here.”

Mary nodded. “I understand.” She held out her right arm.

“It is usual,” said Ponter, “for the Companion to go on the left arm, unless the bearer is left-handed.”

Mary retracted one arm, and extended the other. Ponter busied himself with attaching the Companion. “I’ve been meaning to ask you about that,” said Mary. “Are most Neanderthals right-handed?”

“About ninety percent are, yes.”

“That’s what we thought from the fossil record.”

Ponter’s eyebrow rolled up. “How could you possibly determine handedness from fossils? I do not believe we have any idea what the distribution of hand preferences was among ancient Gliksins on this world.”

Mary smiled, pleased at the ingenuity of her species. “It came from fossil teeth.”

“What have teeth got to do with handedness?”

“A study was done of eighty teeth from twenty individual Neanderthals. See, we figured with those great jaws of yours, you probably used your teeth as clamps, to hold hides in place while you defleshed them. Well, hides are abrasive, and they grind down the front of the teeth, leaving little nicks. In eighteen of the individuals, the nicks angled toward the right—which is what you’d expect if a scraper was being used on the hide with the right hand, pulling the hide in that direction.”

Ponter made what Mary had learned was the Neanderthal “impressed” face, which consisted of a sucking in of the lips, and a bunching toward the center of the eyebrow. “Excellent reasoning,” said Ponter. “In fact, to this day, we hold flensing parties, where hides are cleaned in that manner; of course, there are other, mechanized techniques, but such parties are a social ritual.”

Ponter paused for a moment, then: “Speaking of hides…” He walked to the opposite side of the room, the wall of which was lined with fur coats, hanging, it appeared, from shoulder clamps attached to a horizontal bar. “Please select one,” he said. “Again, those at the right are the smallest.”

Mary pointed at one, and Ponter did something she didn’t catch that caused one of the coats to be released from the clamps. She wasn’t quite sure how to put it on—it seemed to open at the side, rather than the shoulders, but Ponter helped her into it. There was a part of Mary that thought about objecting; she never wore natural fur back home, but this was, of course, a different place.

It certainly wasn’t a luxurious pelt, like mink or sable; it was coarse, and an uneven reddish brown. “What kind of fur is it?” said Mary, as Ponter did up the clasps that sealed her within the jacket.

“Mammoth,” he said.

Mary’s eyes went wide. It might not be as nice as mink, but a mammoth coat would be worth infinitely more on her world.

Ponter didn’t bother with a jacket for himself. He started walking toward the door. This one was more normal, attached to a single vertical tube that let it swing just as though it were on hinges. Ponter opened it, and—

And there they were, on the surface.

And suddenly all the strangeness evaporated.

This was Earth—the Earth she knew. The sun, low in the western sky, looked exactly as she was used to seeing it. The sky was blue. The trees were pines and birches and other varieties she recognized.

“It’s cold,” she said. Indeed, it felt about four degrees cooler than the Sudbury surface they’d left behind.

Ponter smiled. “It is lovely,” he said.

Suddenly, a sound caught Mary’s attention, and for one brief moment she thought perhaps a mammoth was bearing down on them to avenge its kin. But no, that wasn’t it. It was an air-cushion vehicle of some sort, cubic in shape but with rounded corners, flying across the rocky ground toward them. The sound Mary had heard seemed to be a combination of fans blowing downward that let it hover a small distance above the surface, and a large fan, like one of those on the boats used in the Everglades, blowing to the rear.

“Ah,” said Ponter, “the travel cube I called for.” Mary assumed he’d done it with Hak’s aid, and without the words translated into English. The strange vehicle settled down in front of them, and Mary could see that it had a Neanderthal driver, a hulking male who looked twenty years older than Ponter.

The cube’s clear side swung open, and the driver spoke to Ponter. Again, the words weren’t translated for Mary’s benefit, but she imagined they were the Neanderthal equivalent of “Where to, Mac?”

Ponter gestured for Mary to precede him into the car. “Now,” he said, “let me show you my world.”