But the possibility of trade between two kinds of humanity was too significant for Ponter to ignore. Information could certainly be swapped: what Ponter’s people knew about superconductivity, say, for what the Gliksins knew about spaceships. But, more than that, cultures could be exchanged: the art of this world for the art of that world, a dibalat iterative epic, perhaps, for a play by this Shakespeare he’d heard of over there; sculptures by the great Kaydas for the work of a Gliksin painter.

Surely, thought Ponter, these noble thoughts were his sole motivation. Surely he had nothing personally to gain by reopening the portal. Yes, there was Mare. Still, doubtless Mare wasn’t really interested in a being so different from herself, a creature who was hairy where males of her kind were smooth, who was stocky when most Gliksins were gracile, a being with a double-crested browridge undulating above his eyes, eyes that were golden instead of Mare’s own blue or the dark brown of so many others of her species.

Ponter had no doubt that Mare had really suffered the trauma she’d spoken of, but surely that was only the most prominent of many reasons for her having rebuffed his advance.

But no.

No, that wasn’t right.

There had been a real, mutual attraction. Across time lines, across species boundaries, it had been real. He was sure of it.

But could things really go better between the two of them if contact were resumed? He cherished his wonderful, beautiful memories of his time with her—and they were only memories, for his Companion implant had been unable to transmit anything to his alibi archive from the other side. Mare existed only in his imagination, in his thoughts and dreams; there was no objective reality to compare her to, except a few brief glimpses caught by the robot that Adikor had dangled through the portal to summon Ponter home.

Surely it was better this way. Further contact would spoil what they’d already had.

And yet—

And yet it did seem that the portal could be reopened.

Standing in the small anteroom, Ponter looked over at Adikor Huld, his man-mate. Adikor nodded encouragingly. It was time to go into the Council chamber. Ponter picked up the unexpanded Derkers tube he’d brought with him, and the two men walked through the massive doors, ready to face the High Grays.

“The presence here of Scholar Boddit,” said Adikor Huld, gesturing now at Ponter, “is direct proof that a person can pass through to the other universe and return unharmed.”

Ponter looked at the twenty Grays, ten males and ten females, two from each of the world’s ten regional governments. In some forums, males sat on one side of the room and females on the other. But the High Gray Council dealt with matters that affected the entire species, and the males and females who had gathered here from all over the globe alternated in a great circle.

“But,” continued Adikor, “except for Ponter’s daughter Jasmel, who stuck her head through the portal during our rescue operations, no one else from this world has been to that one. When we first created the portal, it was by accident—an unexpected result of our quantum-computing experiments. But we now know that this universe and that one, the one in which Gliksin people dominate, are entangled somehow. The portal from here always opens to that particular one out of the panoply of alternate universes that our physics tells us must exist. And, as far as we can determine from our previous experience, the portal will remain open as long as a solid object is passing through it.”

Bedros, an old male from Evsoy, frowned at Adikor. “So what are you proposing, Scholar Huld? That we shove a stick partway through the portal to keep it open?”

Ponter, standing next to Adikor, turned slightly so that Bedros, at least, would not see his smirk.

Adikor wasn’t as fortunate: he was caught in Bedros’s gaze, and couldn’t look away without seeming disrespectful. “Um, no,” he said. “We have something more, ah, versatile in mind. Dern Kord, an engineer of our acquaintance, has proposed that we insert a Derkers tube through the portal.”

This was Ponter’s cue to unfold the Derkers tube. He got his fingers inside the narrow mouth and pulled. The tube, a latticework of metal, expanded with a ratcheting sound until its diameter was greater than Ponter’s height. “These tubes are used to reinforce mining tunnels in emergencies,” said Ponter. “Once expanded, they resist being collapsed. Indeed, the only way to get one to return to its original size is by using a defastener to undo the locks at each intersection of the crisscrossing metal segments.”

To his credit, Bedros got the idea at once. “And you think one of these will keep the portal open indefinitely, so that people could just walk down it, like a tunnel between the two universes?”

“Exactly,” said Ponter.

“What about disease?” asked Jurat, a local female of generation 141. She was seated on the opposite side of the room from Bedros, so Ponter and Adikor had to turn to face her. “I understand you fell ill when you were in the other world.”

Ponter nodded. “Yes. I met a Gliksin physicist there who…” He paused as one of the High Grays snickered. Ponter had gotten used to the notion, but he understood why it sounded funny; he might as well have referred to “a caveman philosopher.” “Anyway,” continued Ponter, “she proposed that the time lines split—well, she said forty thousand years ago; that’s half a million months. Since then, the Gliksins have lived in crowded conditions, and have bred many animals in large numbers for food. Numerous diseases have likely evolved there to which we have no immunity. And it may be that some diseases have evolved here to which they’re not immune, although our lower population density makes that less likely, I’m told. In any event, we will need to provide a decontamination system, and everyone who travels in either direction between the worlds will have to be treated by it.”

“But wait,” said Jindo, another male, who came from the land south of here on the opposite side of the unoccupied equatorial belt. Fortunately, he was sitting right beside Jurat, so Ponter and Adikor didn’t have to turn around again. “This tunnel between worlds has to be located at the bottom of the Debral nickel mine, a thousand armspans beneath the surface, is that right?”

“Yes,” said Ponter. “You see, it’s our quantum computer that makes accessing the other universe possible, and for it to work at all, it has to be shielded from solar radiation. The huge amount of rock overhead provides that shielding.”

Bedros nodded, and Adikor turned to face him. “So it’s not as though people could travel in great numbers between the two worlds.”

“Meaning,” said Jurat, picking up Bedros’s point, “that we don’t have to worry about an invasion.” Adikor turned to face her, but Ponter continued to look at Bedros. “Not only will individuals have to come through this narrow tunnel, but they will have to make it all the way up to the surface before they can get out into our world.”

Ponter nodded. “Exactly. You’ve reached the marrow.”

“I appreciate your enthusiasm for your work,” said Pandaro, the president of the Council, a Galasoyan 140 female, who, to this point, had been silent. She was sitting halfway between Bedros and Jurat, so Ponter turned left and Adikor turned right until they were both facing her. “But let me see if I understand you correctly. There is no way the Gliksins can open a portal to this world, right?”

“That’s right, President,” said Ponter. “Although I certainly didn’t learn everything about their computing technology, they are a long way away from building a quantum computer anything like the one Adikor and I created.”

“How far away are they?” asked Pandaro. “How many months?”