Solid ground had never felt quite so good.
But she was a long way from safe. When she was sure that her legs would support her weight, she gathered up the rope that was still attached to her climbing harness, coiling it and throwing it over one shoulder, then headed toward an arched passage that led away from the pool. She was about halfway to this intermediate goal when the ghosts began to appear.
The flash of movement in her peripheral vision startled her, as it always did, but once she realized what it was, she tried to ignore the infrasound induced hallucinations. This strategy worked for the length of time it took for her to reach the mouth of the passage. That was when the ghosts started talking to her.
She jumped in alarm, whirling around to face them, positive that this time, there would be a real person there…but the ephemeral phantoms had already retreated to a different threshold of perception.
The voices, like the ghost figures, gave the impression of being real, but lacked the necessary substance. It was not merely that the speech was incomprehensible. The words were not words at all, but tortured unnatural sounds, like someone playing a recording backwards. But then, from the midst of the aural chaos, a single word rang out.
“Jade!”
“Professor! I’m here!”
The stone consumed her shout, absorbing it completely, returning no echo.
The weird cacophony resumed.
“Screw it. There’s got to be a way out of here.” She started forward again, ignoring the figures flitting about in her peripheral vision, paying no heed to the noises that she knew were probably inside her head.
The passage led to a spiral staircase which she mounted without hesitation, charging up two steps at a time, pain and exhaustion as ephemeral now as the hallucinated phantoms.
More real words found their way into the mishmash of sound, as if moving up the staircase was akin to tweaking the tuner on an old analog radio. Garbled static one moment, the next, someone talking plain as day.
“They are my family.” A woman’s voice, but Jade did not recognize it.
“You used me!”
That was Shah. This realization was followed by another far more disconcerting one. There’s someone else in here.
These voices were not auditory hallucinations. She was certain of that. They were real, filtering down through the levels of this strange citadel hidden under the mountain. That meant Shah and Professor had found their way in, but someone had come in after them.
Changelings.
What about Professor? Is he safe? She almost called out again, but realized that if she could hear them clearly, they might be able to hear her as well, and that would ruin any chance of taking them by surprise.
She kept going, consciously trying to lighten her step as she bounded up the stairs. The voices blurred back into random discharges of noise, though once or twice she thought she caught a recognizable word or a hint of the woman’s voice.
The sight that greeted her at the top of the stairs was no hallucination, but that did not make it any more believable.
She had expected another chamber, or perhaps a cramped tunnel snaking through solid rock like wormholes in a sponge. Instead, she found herself surrounded by empty space… or very nearly empty.
She knew there must be cavern walls and a ceiling of stone high overhead, but these limits were beyond the reach of her light. The staircase she had just ascended appeared to rise up the middle of a cylindrical tower, and she now stood at its summit. There were several other towers of varying heights — one of them was probably the shaft she had fallen through after solving the puzzle at the entrance — all connected by stone bridges, but the network of towers was possibly the least amazing thing her eyes beheld.
Aqueducts curled around the towers, supplying water that turned stone wheels and gears, which in turn drove enormous vertical shafts and screw pumps that conveyed water up into the dark reaches overhead. Other structures, which resembled enclosed walkways or perhaps air ducts on a massive scale, wove through the midst of the waterworks, curling around the towers. The curves were reminiscent of a musical instrument. The water and air flowing around the cylindrical towers were creating a veritable storm of resonance frequencies combining in intricate but inaudible infrasound patterns to dizzying effect. In a leap of intuition, Jade realized that the Vault was not some hidden fortress or citadel where the knowledge of the ancients had been secreted away.
It was a machine.
More precisely, it was a sophisticated computer that employed mechanical logic systems, and utilized an infrasound interface.
This realization unlocked a memory, implanted during her experience in the Hypogeum, but incomprehensible without context. She had been here before, though only in a disembodied state. The recollections were not perfect and they did not come all at once, but she grasped, albeit in a very basic way, how the pumps and ducts, and the acoustic design of the towers and indeed the entire underground chamber, functioned. More importantly, she knew where she needed to go next.
She sprinted onto the bridge that led away from the tower and crossed to another. The visual and auditory phenomena chased after her, but it was just so much background noise now. From time to time, she caught a word — Shah or the woman she’d heard before — but never enough to make sense of what she was hearing.
The bridge connected to a larger cylindrical tower that stretched from the cavern floor below to the unseeable reaches above. It might have been a massive support column, but Jade knew it served a far more important purpose. If the vault was a computer, then this was its central processing unit.
An arched opening led inside the cylinder, where she found herself immediately confronted by a choice. To the left, a flight of stairs curled upward, following the curve of the wall. To the right, the stairs went down.
Up felt like the correct decision, so she headed in that direction and bounded up the stairs. She ascended for at least a full minute, the stairs stretching up in the cramped confines of the passage like something from a surreal nightmare. Thankfully, the ghosts and whispers had not chased after her. Something about the composition of the stairwell walls evidently shielded her from the infrasound effects. When she caught a glimpse of a lurking figure, she knew the seemingly endless ascent was nearly at an end. She was not wrong.
The stairs brought her to a wide balcony overlooking a bowl-shaped pit that occupied the center of the cylindrical column. The pit was not deep, in fact it looked to be only about twenty feet from the top of the utilitarian stone guardrail to the bottom. The balcony ringed the pit, and on the opposite side, the stairs continued, disappearing into the space between the outer and inner walls. Overhead, the pit was mirrored by a domed ceiling which, Jade now realized, created yet another spherical chamber.
“If you’re going to kill me, just get it over with.”
The voice startled her, and not just because of its clarity.
Professor?
It was definitely Professor, and what he had just said confirmed her worst fears. He was in trouble. Either Shah had betrayed them and somehow gotten word to his jihadist confederates, or the Changelings had caught up to them.
That question was answered a moment later when she heard Kellogg’s voice, and then the woman she had heard earlier. The voices seemed to be coming from the pit, but Jade knew this was just an acoustical trick. They were close, probably in a room or passage somewhere above this place.
She ignored the not-too-distant conversation and turned toward the rising stairs. She did not know what she would do when she found the others. Judging by Professor’s statement, the Changelings were armed and she was not. Maybe she could distract them and give Professor a chance to gain the upper hand. She would think of something once—