They rushed in and found the key still floating in the beam of light, undisturbed by the blast. Callie couldn’t tell whether it was held between opposing magnets, levitating in some kind of alien stasis field, or hanging from a string. Four of the Liars had been reduced to scorch marks, damaged enough in the explosion to trigger their self-immolation systems, but the last was intact, sprawled unmoving against a wall. “Looks like its suit got damaged in the explosion,” Ashok said. “Must have messed up the self-destruct system.”

  “Is it alive?”

  Ashok prodded the alien with his foot, then shook his head. “Doesn’t look like it.” He crouched and began examining the suit.

  Callie went to look at the key. Her suit’s sensors weren’t as impressive as those in Ashok’s face, but she could tell there was no nasty radiation coming off the key. Didn’t mean there weren’t protective countermeasures in place. She walked around it, marveling.

  The key was exceedingly strange. What had looked like a crystalline sparkle on the viewscreen was much more peculiar than that. The end of the key seemed to change shape, extruding pyramidal spines that then sank back into the central orb, only to reemerge elsewhere – a constant, flowing, eerily beautiful procession of shapes. The Axiom didn’t usually make beautiful things. They made strange things, ugly things, spiny things, wrong things. This key didn’t seem wrong, but it did seem otherworldly.

  “Got it.” Ashok peeled open the dead Liar’s suit, and drew out a sort of bracelet with a greasy-looking black crescent attached to it. “It looks like the same material the wormhole generators we’ve seen are made of, but this one’s not a black box. It’s a black… moon? Scythe blade? Talon? Our death squid was wearing this around a pseudopod, like a bracelet. I bet it opens a portal to that temple place.”

  “Unless it’s the self-destruct button. Remember, when you assume, you’re an asshole.”

  “I don’t think that’s how it goes, cap. Anyway, I found the self-destruct. It’s a unit grafted right into their nervous system, it looks like – if they hit some threshold of damage, or lose muscle control or whatever, whoosh, up in flames they go. The explosion just knocked this one’s unit offline–”

  He stumbled away as the Liar burst into sudden, searing flame, and Callie winced and shielded her eyes.

  “Temporarily offline, apparently.” She stepped toward the remains, which were more intact than usual. The tentacle Ashok had prised from the suit was entirely whole, albeit severed and burned on the end. The explosives must have been threaded through the suit, and since the tentacle was outside containment, it had survived. The Axiom were truly terrible employers.

  “I was just thinking… they didn’t take the key out of here, even though it’s small enough to carry.” Callie picked up the severed tentacle in her gloved hands and carried it over to the beam of light, then pushed it gently toward the key. The tentacle arched, bent, and curved around the beam. She tossed it aside. “They couldn’t touch the key at all. The field pushes them away. The Axiom didn’t trust their employees, or slaves, or cultists, or whatever, no matter how thoroughly subjugated they were.”

  “I wonder if we could touch it? I might be able to disable the security. I’ve seen Axiom barrier fields before, and, unlike these cultists, I’m not brainwashed into thinking the Axiom are infallible unstoppable super-monsters who’ll crush me if I look at them funny. I know they’re occasionally fallible intermittently stoppable super-monsters who’ll crush me if I look at them in any way at all.”

  Callie nodded. “We probably shouldn’t touch it. We should set the last charge and blow this place up, key and all. I don’t trust the Benefactor, but we seem to have a mutual interest in destroying Axiom tech, and they said whatever we found here was a danger to all life in the galaxy.”

  “Huh.” Ashok looked at the key closely for the first time. “I don’t know if blowing up the station would destroy the key. I don’t think it’s entirely in this dimension.”

  “Elaborate.”

  “Look at the head, how it seems to shift and change shape. Given the capabilities the Axiom have demonstrated before, it wouldn’t surprise me if they could create and manipulate extradimensional objects.” He sounded excited, which usually meant he’d found something he wanted to attach to his body, or a way to make things blow up in new and interesting ways.

  “So the key is… like a tesseract?” Callie wasn’t a mathematician but she remembered enough of what she’d learned in school to follow him that far. Tesseracts were theoretical objects that existed in four spatial dimensions, not just the three dimensions she could perceive: they were to three-dimensional cubes as cubes were to two-dimensional squares. Not that she could actually envision what that would look like.

  “Right,” Ashok said. “But I think this is a five-cell, not an eight-cell like a tesseract. It’s a pentachoron.”

  “I don’t know what you’re talking about.”

  “If a tesseract is a four-dimensional cube, a pentachoron is a four-dimensional triangular pyramid, an object bounded by five tetrahedral cells.” He pointed at the emerging and subsiding points. “See?”

  “Not even a little bit.”

  “Hmm. Tesseracts are square-y, and pentachorons are triangle-y.”

  “Okay, slightly better. But what about that makes the key explosion-proof?”

  “Parts of the key aren’t in this dimension to be blown up, is the thing. Imagine you’ve got a whale with its head inside your house–”

  “Ashok, your metaphors are horrible.”

  “You could blow up the house, right, and destroy the whale’s head, but the rest of the whale’s body, sticking outside, would be fine. Apart from being dead I guess. Anyway. Now imagine you can’t even perceive the world outside your house.” He paused. “Maybe it’s not such a good analogy, I concede, but do you get what I mean?”

  “Yeah, I get it. Even if we destroyed the visible part of the key the rest of it would be fine.”

  “I really shouldn’t have mentioned the whale. There’s a good chance nothing we do would affect this key, if it’s a key, at all. It could be indestructible, unless you have an interdimensional anvil and hammer and tongs.”

  “So how do we get rid of it, assuming it’s a dangerous weapon we need to eliminate?”

  “We could hurl it into a star.”

  Callie nodded. “That will destroy most things.”

  “Well, no, that wouldn’t destroy it either, but at least then the key would be in a secure location. Nobody’s going into a star to get the key back.” He paused. “Unless the Axiom have technology that allows them or their servants to go inside stars. Not ruling it out.”

  “Hmm. Even if we blow up the station, the key will probably just remain here, unharmed?”

  “It might just keep drifting in space, yeah.”

  “So sending us here to blow this place up might, theoretically, have been a way to clear out all the obstacles between the Benefactor and the key, so they could swing by and scoop up the floating extradimensional object of their desire after we left, with us none the wiser.”

  “You have a suspicious mind, Callie. That’s why you’re the boss.”

  Callie sighed. “Do you think the key actually opens anything?”

  Ashok held up the black crescent on the bracelet. “I kind of do. Maybe something on an unknown planet.” He grinned. “It’s been ages since we opened a mystery box. Could be gold in there. Could be spiders. But don’t you want to know?”

  “It has not been ages since I made a dangerous decision driven by curiosity. It’s been, like, a month. But all right. See if you can lower that field.”

  “Sure. But first–” Ashok reached into the pillar of light with his left hand… or tried to. His fingers hit resistance. He gritted his teeth and pushed, then sighed. He tried with his right hand, the one with manipulators instead of fingers, and had no more luck. “Oh well. Worth a try.”

  “Was it? You could have lost your hand!”

  She couldn’t tell, because of his complex optics, but Callie was sure he rolled his eyes anyway. “Oh no. Whatever would I do. I’d have to get an amazing new hand, maybe with that integrated miniature cryo-beam I’ve been working on with Lantern. What a potential tragedy we have narrowly averted.”

  “You’ll never get promoted, talking to your captain like that.”

  “I’m okay with ship’s engineer being my terminal rank. Ambition was never my problem. Guess we go with our original plan, huh?” He knelt to place the last explosive charge, this one right on the base of the pedestal that held the key.

  “Maybe it’ll destroy the key anyway,” Callie said.

  “We’ll find out,” Ashok said.

  They blew the station from the White Raven, and watched it explode into small fragments from a safe distance.

  “I’m not seeing anything unusual in the debris field,” Janice said. She was half the cockpit crew, running communications and the sensor array, and was famed for her ability to inject just the right note of despair and cynicism into any conversation, no matter how hopeful. “You probably ran low on oxygen and hallucinated this magical key.”

  Drake, the pilot, was her other half – not in the sense of romantic involvement, because they weren’t, but in the sense of sharing a body with Janice, which he did. Years ago they’d been in a catastrophic spaceship accident, and should have died, but an unknown group of Liars with a propensity toward medical experimentation had put them back together again from their surviving parts and mysterious tech. Drake, being the more optimistic of the pair, thought the aliens had meant well, and just hadn’t known what humans were supposed to look like. Janice held that the Liars were mad scientists amusing themselves with human experimentation. “Could be floating there, hidden in the mess,” Drake said. “It’s small.”

  “True,” Janice said. “I haven’t run diagnostics on my magic key detector in ages either.”

  “Shall,” Callie said from her seat at the tactical board. “Send a drone out to look for anything that scintillates and coruscates, would you?”

  Shall, the AI that ran the ship’s computer – sort of was the ship’s computer – said, “Will do. It’s been ages since I went outside.”

  CHAPTER 3

  Callie and Ashok were floating in the cargo bay as the small drone returned, bearing the key in its manipulator arms. “Just floating there, unharmed, as you predicted,” Callie said. “Think it’s safe to touch?”

  Before she could stop him, Ashok gripped it in his manipulators, then tapped the shaft gently with one bare finger of his other hand. “Feels like glass. Cool and smooth. I would avoid touching the in-and-out-of-reality triangles though. You might lose a finger.”

  Callie took the key and held it up, watching its teeth dissolve and erupt. “Those Liars were willing to die to protect this. They’ve been guarding it for millennia, probably, passing on the directive to guard it to generations of babies.”

  “Let’s see why.” Ashok stroked the greasy-looking crescent he’d strapped to his wrist, and a slit appeared in the air. “Activates just like the short-range teleporter.”

  Callie sighed. “Please don’t open holes in space-time on my ship again without asking first.”

  “You don’t want to go?”

  She sighed again. “Shall, let everyone know Ashok and I are leaving the ship to check something out.”

  “Are you taking the canoe?” That was their small boarding-and-landing vessel, currently in the cargo bay.

  “No, we’ve got an Axiom toy that opens doors in the air.”

  “Better go quick before Elena finds out,” Shall said.

  Elena Oh was the ship’s executive officer, doctor-in-training, and the love of Callie’s recent life. She was generally very supportive, but even she had her limits, and Callie thought this might just brush up against them.

  Ashok gestured at the tear before them. “Rank has its privileges.”

  Callie took a breath, then moved through the slit. It was nothing at all like passing through a wormhole bridge. It was much more like pushing through a curtain made of rotting meat. Even through her spacesuit, something about the texture of the ragged air, pliably giving way against her body, made her shudder.

  Ashok followed and the slit sealed up behind him. He looked at the screen on his arm and whistled. “This is… we’re in the same place we were before. Like, coordinates-wise.” He looked around. “Cap, I think we’re in the fourth dimension.”

  Callie looked around. Fluted pillars, white walls etched in what she now recognized as the eye-twisting script of the Axiom, a smooth white floor, and that dome overhead, the alien sun a little lower now. “Up, down, side-to-side – I still just count three dimensions, unless you include time, which we’re wasting. Besides, I don’t remember much undergraduate math, but I know the fourth dimension isn’t a place, it’s a dimension of space we can’t perceive.”

  “Yes, true – I was being dramatic, but the situation warrants it. We’ve moved from our local space-time into a… not adjacent, exactly, but overlapping? No, that’s wrong too. This thing doesn’t teleport us, at least not to another point in our space-time. It doesn’t make a wormhole. It’s a phase-shifter. The Liars were using them to sneak up on us, ducking in here, then emerging in another place in our usual spatial reality.” He looked around. “I wonder how they control where they come out.” He touched the crescent and another opening appeared, showing their cargo bay. He sealed it up. “Opens in the same place we left from. Good, but boring. Hmm. This looks like the same room I glimpsed through the portals on the station, even though we’re kilometers from that position. I don’t think this place bears any relationship to our spatial coordinates. It’s some kind of pocket universe.”

  “A pocket universe with its own sun? Seems a lot more likely we’re in an unknown system.”

  Ashok looked at the ceiling and whistled. “Look, there, and over there.” He pointed. A couple of small panels in the immense dome were black. “I think you’re right. I think that dome is a viewscreen, just projecting an image. Maybe that moonscape is where the cultists used to live, or something. I don’t believe there’s really a sun or moon outside.”

  “Then what is outside?”

  “Um. Possibly… nothing. Literally nothing.”

  “I’m not sure that makes any sense,” Callie said.

  “Me either, to be totally honest – I’m an engineer, not a theorist. But we’re here, and I don’t think here is a place you can get to in a spaceship. It might not even be a real place, as we understand places. And reality. This could be an Axiom construct, a little extradimensional hideaway created to keep… That.”

  He pointed past her. Callie turned, and whistled. There was a vault door set in the wall behind her, an archway of golden metal five meters high and three meters across, with a hole in the center about the height of her head and the size of her fist. She looked down at the still-shifting key. “You think this key opens that door?”

  “Occam’s Plasma Grenade.”

  “But a lock, and a key, it’s so… old-fashioned. The Axiom could manipulate constants of space-time. Why would they lock something in a vault?”

  “A vault hidden in another dimension, with a key that exists in multiple dimensions. Why not? That vault’s not hooked up to any kind of computer system, so it can’t be hacked. I’m guessing the biggest bomb we’ve got wouldn’t put a scratch on it – it’s probably extradimensional too. You can’t pick that lock, unless you have lockpicks that exist in four dimensions, and I don’t. One key, to open one vault, protected by self-destructing zealots. We would never have gotten here with the key if the Axiom hadn’t abandoned that facility, for whatever reason, however many centuries ago, and let their operational security go to shit.” He grinned. “So do we open it?”

  “The Benefactor’s message said this station was one of the most dangerous Axiom facilities in the galaxy,” Callie said. “Given some of the things we’ve encountered… that sounds pretty dangerous. The Benefactor told us this station should be destroyed, for the sake of all life in the galaxy. Or it could have been a trick to get the key so the Benefactor could open the vault and get whatever’s inside. Either way… I doubt there’s anything nice behind that door, Ashok.”

  “But it’s a vault, and we have a key. How can you not be tempted?”

  “I never said I wasn’t tempted.” Ashok’s curiosity was notorious. He’d fly into an exploding starship if he thought there was interesting tech hidden inside. Callie was more pragmatic… but she was also vulnerable to the allure of the unknown. Her ex-husband used to say Pandora had nothing on her – Callie would have opened that box without hesitation. “But just… imagine you’re an alien, and you land on Earth, and you find a mountain, and there’s a steel door in the mountainside. The door is covered with pretty little symbols, triangles inside circles… all in yellow and black. You might be tempted to look inside, but it would be a bad idea.”

  “You think there’s toxic waste behind that door?”

  “I think the Axiom fought wars with each other that destroyed star systems. I think they launched long-term projects designed to alter fundamental characteristics of space-time – some of which are still ongoing thousands of years later, as we’ve discovered. I think they plotted to survive the heat death of the universe. I think anything they locked up, with a key like this, in a place like this, could be something we don’t want to fuck with.”

  “It could be something amazing.” He gazed up at the door, and then frowned. His mouth was still human enough for that. “Huh. There’s more writing up there, over the door.”

  Callie tilted her head back, and saw more of the Axiom script, following the arch above the vault. “Can you read it?”

  “Lantern taught me some of the language, and I’ve got a visual dictionary loaded in my external memory. I recognize most of the words… let me see… that’s the imperative case – no, wait, it’s got a warning inflection, hold on. I think it says something like… ‘Open only on the last day of the war.’”