“But adverts…” Auger was finding it difficult to keep a straight face.
“Think about it. Anyone travelling along one of these links is the perfect captive audience. They’re locked in, sucker bait. Got nowhere else to go, no other scenery to look at. What better place to put some advertising? Hell, I’d love to know what they’re selling. Maybe it’s planet-building services, or stellar renewal, or the option to trade in your old black hole for a new one.”
Auger smiled. “A supernova can happen any time. Make sure your solar system is properly insured.”
“How about: tired of the Milky Way? Why not look at some of our great properties in the Large Magellanic Clouds. The best views in the local group—and it’s still within commuting distance of the galactic core.”
Auger chuckled, getting into it. “Expansionist primates infesting your stellar neighborhood? We have the pest-control solutions you need.”
“Your old God not up to the job? Upgrade your deity now by calling…” Skellsgard started giggling.
“You’re right—it’s almost believable, isn’t it?”
“Almost,” Skellsgard said. “And I definitely prefer it to theory four.”
“Which is?”
“That the walls are covered in graffiti.”
“Goodness.” Goodness. Had she really said “goodness?” Auger shook her head, like someone about to sneeze. “Are you telling me that somebody’s actually been paid to come up with that?”
“Yes. It even makes sense based on the Shannon entropies, apparently. If you look at human graffiti—”
“Enough, Skellsgard. I’d rather not hear about graffiti, human or alien.”
“It’s a bit depressing, isn’t it?”
“More than a bit.”
“Well, don’t worry about it,” Skellsgard said, waving a hand dismissively. “Not many people take it very seriously. There’s the small problem that the tunnel patterns have a habit of changing, depending on stability conditions. Of course, it might be very clever graffiti—”
“Is there a theory five?”
“Not yet. But I’m sure someone’s working on one.”
Auger laughed. Everything she knew about academia told her how true that was. Skellsgard’s composure cracked as well, and it was only when they finished laughing, sighing with exhaustion and their eyes wet with tears, that Aveling opened his eyes and stared at them, his face as impassive as ever.
“Civilians.”
In the twenty-ninth hour, something changed in the spiderweb crawl of Skellsgard’s stress-energy display. The contours began to arrange themselves in a systematic and intricate pattern quite unlike the asymmetric bunching and stretching caused by the tunnel markings.
“You might want to look at this,” she said.
“Is something wrong?” Auger asked.
“No. We’re just coming up on something a little unusual, that’s all. We always hit it somewhere between the twenty-eighth and twenty-ninth hours, although it’s never in quite the same place from trip to trip.”
“More graffiti or tunnel turbulence?”
“Nope. Much too stable for that.”
Auger leaned forward, relaxing her seat buckle. She kept her voice low. Aveling was asleep, snoring lightly, and she had no particular desire to wake him up. “So what are we looking at?”
“We’re approaching a widening in the fabric of the tunnel. It’s like a bubble, somewhat elongated in the direction of travel.” Skellsgard made a few micro-adjustments to their flight path, signalled by a sequenced volley of steering jets. “At first, we didn’t know what to make of it.”
Auger tried to make some sense of the slowly moving contours, but she suspected it would need weeks of practice to untangle the information into anything approaching a three-dimensional image of their surroundings.
“And now?” she asked.
“We call it the ‘interchange cavern,’ ” Skellsgard told her. “As far as we know, the Slashers have never found anything like this in any of their travels. All the connections they’ve mapped have been simple point-to-point affairs. You might get multiple clusters of portals located close to each other in space, but you never get junctions in the hyperweb threads themselves.”
“Except for this?”
“Well, there’s obviously something special about this link because it feeds into the heart of an ALS. We think the interchange cavern allows selective access to different points in the crust of the captive planet.” With one blunt fingernail she tapped particular features in the contour display. “There are nineteen possible routes out of the cavern, as far as we can tell, not counting the one we just arrived by. Trouble is, our steering control is only sophisticated enough to allow us to change course in time to reach six of the exits. Of the remaining thirteen, we’ve managed to drop lightweight instrument packages into four of them, but we never heard anything back. They probably didn’t even make it to the ends of their threads.”
“What about the six exits you can reach?”
“We always come out underground, within a few hundred metres of the surface. But five of the six exits are no use to us. Given time, we could tunnel our way to daylight, but it would take years, and every kilogram of rock we excavate would have to be brought back through the link.”
“I’m missing something here,” Auger said. “What’s so difficult about digging through rock, given that you’ve already excavated half of Phobos?”
“There’s a catch: our tools don’t work on E2. We’d have to dig our way out with our fingers.”
Auger asked the obvious question. “Wait. If you can’t reach the surface, how do you even know it’s the same planet? What if the threads lead somewhere else entirely?”
“Gravity’s the main clue. It’s always within a per cent or two of the same value, no matter where we pop out. Geochemistry varies a little, too, but not enough to lead us to think we’re inside a different planet each time. We can plot these data points against our knowledge of E1 and take a stab at figuring out where we are—at least to within a continent’s accuracy—but only one exit lets us reach the surface.”
“Because it’s closer?” Auger asked.
“No. Because there’s another tunnel right next door. We only had to dig through a few dozen metres of actual rock before we hit a pre-existing shaft. If it wasn’t for that…” Skellsgard’s expression became philosophical. “Well, Susan would still be alive, and you’d still be looking at a tribunal.”
“Thanks for the reminder.”
“Sorry.”
They passed through the interchange cavern without incident. Less than an hour later, Aveling’s sensors began to pick up the reflections from the approaching throat: the faint echo from the same kind of bow shock wave that had signalled the arrival of the other transport in the Phobos cavern. He told Skellsgard and Auger to secure themselves for arrival, which meant additional seat restraints and webbing, tightened to the point of discomfort. Auger recalled the violent arrival of the ship in Phobos and prepared herself for the worst.
When it came, it was mercifully quick, and she had no sooner registered the fact that the ship was slowing than she felt the arrestor cradle clang into position around the hull. The ship surged forward, halted and then lurched back as pistons took up the recoil. And then suddenly all was very calm, with Aveling reaching above his head to flick switches, powering down vital systems.
Auger had weight now, an unwelcome burden after thirty hours in free fall. It was an effort to move her arms to undo the seat harness, and a struggle to lift herself from the seat. Her muscles protested for a few moments as she began to stretch, and then, sullenly, resigned themselves to the task.