On the cliff, the wind blew through Ty’s hair and tugged at his clothes. He stared at the four figures.

“Why did you send the broadcast?” “You already know, Ty.”

“You needed our help.”

The figure inclined its head slightly.

Ty pressed on. “You needed us on that world—to stop the Covenant.” “Correct again.”

“Why can’t you do it yourself? You clearly have far more advanced technology than we do.”

With the previous questions, the figure had answered instantly. Now the group fell silent, the only sound the howling wind whipping across the rock face.

Behind them, the air changed. It rippled and coalesced.

A figure appeared, also wearing a suit with a mirrored helmet, except the material of the newcomer’s suit was gray.

One of the four suited figures who had brought Ty to this world quickly brought a hand up to the quantum radio medallion on their chest and dialed.

Once again, the world disappeared.

In the next second, Ty was standing in a forest with massive trees. They were wider and taller than any redwood he had ever seen but with similar bark, leaves, and cones.

Unlike the cliff where they had been a second before, it was quiet except for the creaking of the forest as a twig or branch fell. Fog drifted among the trees like groups of ghosts parading through.

In the distance, there was a soft boom. The ground trembled.

The four figures stood near one of the towering trees. Ty could still feel Nora’s hand gripping his.

In his peripheral vision, he saw Kato spinning around, taking in their surroundings in every direction. Ty assumed he was scanning for threats.

Maria was breathing rapidly. Nora reached out and took her hand, silently trying to calm her.

“What was that?” Ty asked.

“Covenant agents,” the closest figure replied. “They’re hunting us?”

“Yes. But we’re dealing with it. We may have to change Way Stations again.”

“Way Stations?”

“A world like this one. An Earth without humans but with a breathable atmosphere. There are no threats to you here.”

“Except the Covenant.” “Only if they find us.”

“Back up,” Ty said. “Who are you?” “You can call us quantum historians.”

Ty squinted, unsure what to ask next. “Where are you from?” “We’re from the same place as you, Ty.”

“Earth.”

“Correct. But the Earth we evolved on is different from yours. Not radically different, but different enough to matter quite a bit. Our civilization was slightly more advanced than yours in one important way: when your world was developing the atom bomb, we were experimenting with quantum technology. Our world was one at peace. A single global society with a shared purpose: to use science to unravel the greatest questions of human existence. In the subatomic world, we saw the thread that we could pull to unravel these mysteries that haunted us. What we didn’t know then was that our discovery would be our undoing.”

In the distance, the booming started again, growing closer. The figure ignored the sound.

“Our great discovery was that via particle collisions, we could make the membranes between universes porous. At first, we sent other subatomic particles through.”

“Like you did to our world,” Ty said. “The quantum radio broadcast.”

“Precisely. We used what you would call entangled particles. We sent one of the entangled particles through the pores between the universes and kept the other on our end. When we manipulated the particle in our universe, it

changed the state of the entangled particle in the other one. This process required an exceptional amount of computing power and energy, but it worked.”

The ground trembled again, and Ty, Nora, Kato, and Maria all turned to look, but there was only a cloud of fog moving across the trees.

“Pay no mind to that,” the figure said. “It’s no threat to us.”

“What is a threat to us?” Ty asked. “Why are we hiding in this Way Station?”

“You’ve seen already. On the A21 world. And your own. And just now.” “The Covenant.”

“Correct.”

“Who are they? What are they?”

“They are not so different from us. Or you. We found them by accident. As I said, we began our venture into the multiverse through a series of entanglement experiments. Soon, they grew tiresome. The answers they yielded were less profound. We wanted to know more about the multiverse. To observe and explore. And importantly, we had no fear of what we might find. Scientifically, we had no equals. We were sublimely clever, but we had a disastrous flaw.”

“You were naive.” “In the extreme.”

The figure who had been speaking paused, as if listening, then turned to one of the other figures and froze.

Ty assumed they were communicating via some wireless mechanism in the helmets. It looked like an argument.

The lead figure turned again and resumed speaking, the grating, computerized voice a sharp contrast to the serene forest.

“We soon discovered that with the right collisions and particles, we could vastly enlarge the pores between the universes, dilating them enough to send matter through. We sent rovers. We lost more than we could count. We soon discovered that across the multiverse, life on Earth was the exception, not the rule. And so was an atmosphere survivable by humans. Yet we persisted. We made a sort of map of the multiverse, marking the Earths that were hospitable to human life. They were rare too. And on those habitable Earths, every now and then, we found one populated by humans.”

The figure paused. “You might think that means there aren’t that many inhabited Earths. But the nature of infinite numbers dictates otherwise.

While only a very small fraction of these worlds were inhabited, there are an infinite number of universes, and because even a small fraction of an infinite number is itself an infinite number, there are, thus, an infinite number of inhabited human worlds, more strange and varied than you can imagine. And some so similar to your own that you’d have to study them a lifetime to find even the tiniest difference.”

The figure took a step deeper into the forest, toward the nearest cloud. “In the multiverse, we found our purpose. We saw a role we were singularly qualified to perform: cataloging the quantum realm. We were scientists. We are still scientists. We set about taking a scientific inventory of the multiverse, observing and documenting all of the habitable Earths and the humans that lived on them. The ranks of the quantum historians grew as more members of our society used quantum radio medallions to port to unexplored worlds. We had a rule for any historian traveling the multiverse: never interfere. We were—and remain—observers only. We saw no other way.”

A cloud of fog drifted between the two groups. When it had passed, the figure spoke again.

“For years, we believed that we were the only ones to discover the door between universes. A few of the human-populated worlds we encountered were more advanced than us in other fields: medical technology, nanotechnology, space exploration, artificial intelligence, immortality, telepathy, and telekinesis. We had our strengths. They had theirs. Our particular ability simply allowed us to visit them. In fact, we found worlds with technologies and wonders so breathtaking I cannot now describe them to you—for your own sake. But no matter how advanced or different from us, we never met another human society that was our equal in the quantum sciences.”

The historian paused. “As such, we assumed we were the only humans moving across the multiverse. And no world was ever able to detect our presence. This was the case for years, until a team of quantum historians was observing a world populated by Neanderthals who had built an advanced society. The Neanderthals couldn’t detect our presence, but the team quickly realized that there was another group of observers on the planet—using technology similar to ours. At first, they thought there had been a scheduling error—that there was simply another team of quantum historians present. But when they made contact with the other team, they

quickly learned the truth: they were not from our world. For the first time, we made contact with a civilization capable of traveling the multiverse like us. Another group of observers. It was an incredible discovery.”

Ty swallowed. “Let me guess: this other group was the Covenant.”

The figure inclined their head slightly. “Indeed. Whereas we called our teams quantum historians, the Covenant called their teams quantum agents. Our activities, however, were much the same: mapping the multiverse and cataloging the vast eventualities of human possibility. In the Covenant, we believed we had finally found a kindred spirit, another ship in the night, an equal to share the joy of exploring the multiverse.”

The ground trembled again. Three booms sounded, closer now. Ty wanted to look back, but he found himself captivated by the quantum historian’s story.

“We visited the Covenant world, and there we saw what appeared to be our mirror world. It was something we had long sought—a world we thought we could learn from. And we did. What we didn’t know then, in the joy of meeting them, was the heavy price we would soon pay.”

“What kind of price?” Ty asked.

“The ultimate price,” the historian answered. “Lives. And possibly, the future of our society.”

“What happened?”

“As I said, in the Covenant, we believed we had found a kindred spirit. A society with our quest for discovery and knowledge—and quantum technology as advanced as our own. Together, we traveled the multiverse, making observations and returning home to share our discoveries with a waiting public that was fascinated by the findings. We shared our data with each other like two friends with the halves of a treasure map, embarking on the ultimate adventure together. What we didn’t realize was that the Covenant was different from us in a small but important way.”

Behind Ty, the booming sound grew louder. The cadence of the pounding had stopped before, but now it persisted, growing closer, louder, the ground shaking.

Nora squeezed Ty’s hand.

They turned in unison just as a cloud of fog cleared. The trees towering above swayed as the giant beast came into view.

The animal had four legs like tree trunks, round, stubby, and heavy. Its body was covered in leathery brown skin. It must have been three hundred

feet long, with a tail a third of the length of its entire body and a neck about half that. Its small head turned lazily to look at the eight small figures standing in the forest below.

Ty stared up in awe at the dinosaur.

Brontosaurus: that was the name his mind supplied, but he knew this dinosaur was likely different from the one that had lived on his Earth so long ago.

The magnificent creature raked its eyes over the group on the ground and merely glanced away, as if it had seen a few bugs. It marched forward, chewing a mouthful of plants, the ground shaking less as it moved on.

The quantum historian spoke again, drawing everyone’s attention.

“What we didn’t realize was that the Covenant saw the multiverse differently than us. As I said, we were naive, and at first, this nuance in their perspective wasn’t apparent. And we didn’t know to look for it. To us, we were simply a pair of vessels upon the quantum sea, charting a course together, sharing in the discoveries. But where we saw the islands and the animals and the fish in the ocean as things we would never interfere with, the Covenant saw something entirely different. We only learned what they saw after an event on the Covenant home world we call the Cataclysm.”

The historian spread their hands. “After the Cataclysm, the Covenant ventured out into the multiverse not as explorers, but as exploiters. In the worlds of the multiverse, they saw their only means to save their homeworld. Their voyages became not missions of discovery, but missions of change—efforts to alter worlds in ways that could help them overcome the Cataclysm.”

“That’s why the Covenant is interfering in our world,” Ty said. “Yes.”

“And the one you brought us to.”

“Also correct. They are preparing both worlds for harvest.” “Harvest of what?”

“It varies by world—and in truth, on some worlds, we’re not quite sure what the Covenant is doing. On the world you just saved, their objective was clear.”

“The troops.”

“Correct. They were building an army—we assume to bring through to another world for warfare. You stopped that.”

The Brontosaurus’s footfalls were faint now, the cadence regular as it paced away. Ty let a few of the booms echo in the forest, and then asked the question that was bothering him. “Which brings us back to my previous question: why didn’t you? It’s clear you have the technology to stop them. If you’ve visited countless worlds in the multiverse, it seems like you’re a good bit more qualified than the four of us to stop a world war.”

“We can travel across the multiverse, and we can alter entangled particles on a small scale, but it’s not enough to stop the Covenant.”

“Why?”

“For one, countering Covenant operations requires understanding what they’re trying to do. But it’s more than that. Effecting change on a macroscopic scale requires direct intervention.”

Ty smiled. “You seem as capable as us.”

“In many ways. Physically. Scientifically.”

Kato spoke then: “You didn’t want to get your hands dirty. Or, in this case, bloody.”

“Those are not the words we would use,” the figure said. “But it’s the truth, isn’t it?” Kato asked.

Ty took the silence as confirmation by the historians.

“Why lead us to the A21 world?” Ty asked. “Why not send us a message asking for help?”

“Consider it a moment, Tyson, and you’ll see the answer.” “You were testing us.”

“We were. The world you just left, the A21 world, was a test of your abilities, and most importantly a test of your morality. We wanted to know what you would do when a dying man was laid at your feet. And how you would react when you knew that you were the key to saving a world that wasn’t your own. Would you risk your own lives for them? For strangers? You could have tried to use the radio to get home, but you didn’t. You were disciplined, and you worked together as a team. Even in the face of long odds, you took risks to save those strangers, and you stopped the Covenant on that world.”

“Again, all things you could have done yourselves,” Kato said.

“We are pacifists. We have been for a very long time. Recruiting quantum intervention agents from our world would violate the core beliefs of our society.”

“But it doesn’t bother us,” Ty said. “We grew up in a world of both violence and peace. You need us because we’re capable of doing what you can’t—stopping the Covenant and making a mess in the process if that’s what it takes. In a way, we’re the middle ground between your society and the Covenant. We’re capable of changing worlds, like the Covenant, but we care enough to save them—like you. That’s really why you need us.”

Before the historian could answer, waves formed near one of the giant trees and the air began sucking in. Just as a Covenant agent appeared, the forest vanished.