By touch, Agata confirmed what she’d guessed by sight when the grille had been illuminated: the bars really were embedded in the wall, continuing right into the surrounding stone. The masons must have drilled one hole straight, but created a whole triangular cavity at the opposite point, allowing a rod that was too long to fit directly across the tunnel to be inserted at an angle and then made true. They would have packed the cavity with sand and adhesive, and over time it would have set into something almost as strong as the surrounding calmstone. But though the bars themselves were close to unbreakable, calmstone was just calmstone. Agata put the point of her hand drill against the wall beside the longest of the bars and set to work enlarging the hole that contained it.
By the end of her shift she’d made slots that allowed her to remove and replace three of the bars at will. Two more, and she’d be able to squeeze through.
Agata packed up her tools and forced herself to swallow them again. Beyond the half-disassembled grille and the last segment of the tunnel, there’d be another grille just like it guarding the outlet from the chamber itself. She’d need more time to transit that segment, but the task no longer seemed impossible.
Agata ground the roots with the mortar and pestle she normally used for spices, feeling like some kind of demented kitchen alchemist. The flowers she’d cut up were all decorative species that had been planted around the beds of travellers for generations, in a relic of the old folk belief that their petals’ light had health-giving properties. She had never gone in for the custom herself, but at the garden no one had questioned her. The assistant had invited her to pick whatever she liked.
Every plant root contained substances that bound to a range of minerals. Over the generations, chemists had painstakingly tabulated their properties, species by species, and the appendices to Agata’s school chemistry textbooks were full of such quaint pre-photonic compendia.
The effect she was hoping for was not dramatic; she didn’t need a liberator to set the sunstone in the cooling chamber on fire. All she had to do was ‘poison’ a large enough portion of the surface of the rock. The size of the air particles that the sunstone produced was sensitive to the amount of time the decomposing agent spent in contact with it; if she could weaken the agent’s binding, some lighter air than normal would be produced. The total volume didn’t have to be enormous; the giant centrifuge of the Peerless itself would separate out the less massive component, concentrating it preferentially around the axis.
If she could get enough disruptor into the cooling chamber, the next step would be verification. She would need to be able to quantify the effect of her intervention on the refractive index of the air near the axis, not least to be able to convince Ramiro and Tarquinia to abandon their own efforts. The shift ought to be measurable in principle, but it would require specialised, high-precision instruments. Agata had no idea how she could get her hands on equipment like that without attracting attention – but she was sure that, like every other aspect of the plan, if she remained resolute it would fall into place.
‘You get keener every day,’ Celia observed. ‘I can move you to an earlier shift if you like.’
‘No, this is perfect.’ Agata wasn’t sure how much explanation her early starts required. ‘I just have trouble planning the journey sometimes; if I’m not as energetic it can take me a few more lapses to get here, but if there’s any doubt I’d rather make sure I won’t be late.’
‘Hmm.’ Celia didn’t care. ‘Any new thoughts about the disruption?’
‘I’m still optimistic,’ Agata replied cautiously.
‘You’ve seen the ancestors’ writing,’ Celia acknowledged. ‘Of course that makes you hopeful. But they didn’t tell you how many of us survive.’
‘But nor did they mention a great tragedy,’ Agata replied. ‘They just offered their thanks. If the mountain had been shattered, you’d think they would have aimed for a higher level of solemnity.’
Celia was amused. ‘Six generations on? It will all be ancient history by then. They’ll carve their memorial on Esilio and some politician will make an empty speech.’ She handed Agata her tool belt and access key. ‘No one will know what our lives were really like, and no one will care.’
Agata said, ‘Perhaps.’
Agata forced herself to complete a full sweep of the tunnel, burning off every visible speck of moss. But as she raced back towards the site of her real work, when she noticed one faint red smudge that she’d missed she did not stop to pull her coherer from her belt.
She paused to disassemble the centre of the first grille, then she slipped through and continued down the tunnel. Her fellow worker who came here on an earlier shift had left a few mossy smudges of her own; no one was perfect. Agata reached the second grille with almost a bell to spare. She reached into her gut and pulled out her tools. The package was tied by a string to her first canister of disruptor.
Working on the grille in utter blackness was pure instinct for her now; her fingers gauged the narrow trench left by her previous assault and guided the drill to the right location with no intervening thought. Between bars, she only stopped to check the clock on her belt.
When she’d eased the fifth bar out and laid it on the floor of the tunnel beside her, she hesitated. Maybe there were invisible defences around the outlet – vibration sensors and high-powered coherers. Before the bombing that would have been unlikely, but anything was possible now.
Agata reached through the grille and sent one of the bars skidding towards the outlet. No weapon’s flash broke the darkness. She only had a few chimes left in her shift, and four days before her most optimistic deadline for starting the diffusion. If there ever was a time to take courage and tell herself she was untouchable, wrapped in the arms of the ancestors, this was it. She crawled through the broken grille.
She’d thought she’d grown accustomed to the blasts of chilly air, but as she crossed the last few strides each wave of pressure felt like a physical assault. She switched on her coherer at the lowest possible brightness and squinted into the machinery where the tunnel began.
In the chamber below her, the pressure of the newly formed gas was increasing, forcing the piston up along the outlet shaft. She could see the great polished stone cylinder rising now, the side of it completely blocking the tunnel, its motion only visible from flaws and scratches rushing by.
Then it cleared the mouth of the tunnel, and the cold air from the chamber came rushing out. Agata felt every hardened patch of wizened skin on her body forced into the flesh beneath, with the chill only sharpening the sensation.
As the pressure driving it plummeted, the piston stopped ascending and came hurtling down. Agata had known the rhythm of the full cycle from the first day she’d crawled into the tunnel, but what mattered now was the exact time the outlet shaft was exposed. She crouched before the piston, utterly attentive, letting the process imprint itself on her, binding every visual and tactile cue into a single act of perception.
She closed her eyes, waited for the moment, opened them: and there it was, the bottom of the piston rising up. She couldn’t lose it now, she couldn’t get it wrong.
Agata drew the canister of disruptor out of her tool belt, and unscrewed the lid to the point where one more quarter-turn would free it. A single knock would spill the contents, but mere passage through the air would not; she’d tested that a dozen times.