The Arrows of Time

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.

She closed her eyes, waited, then opened them. She hadn’t lost the rhythm. Every muscle in her body knew what to do, and when.

The piston plunged, the pressure rose. Agata waited. The piston ascended.

As the piston rose above the mouth of the tunnel, she threw the canister. It entered the shaft and disappeared. She heard no sound from the impact, but she hadn’t expected one; the bottom of the chamber would be far below, and the canister might yet be spinning in mid-air, still caught in the updraught.

The piston crashed down again, closing the mouth of the tunnel. Agata closed her eyes, overcome with relief. She had four more days; she could prepare and deliver at least four more doses. All her numbers were approximations and guesswork, but unless she had wildly miscalculated, that total would at least give her a chance.

The air burst out from the chamber once more; Agata opened her eyes to welcome it. A trace of fine grit stung her eyes, then something clattered loudly across the tunnel floor.

The canister came to a halt beside her. She stared down at the rejected gift. If it had travelled all the way into the expanse of the chamber, it was very unlikely to have entered the shaft again.

There had to be a grille or baffle of some kind at the bottom of the shaft – below the piston’s lowest point, or the canister would have been crushed into powder. Some of the disruptor would surely have ended up inside the chamber, but the grit blown back at her must have been the rest.

Agata touched the clock on her belt; she needed to start moving immediately, or she’d be so late for her end of shift that Celia would send in a search party. She gathered up her tools and the lidless canister and forced them back into their hiding place.

She had four days left, and a barrier at the bottom of a giant, pounding piston that would reject most of what she threw into the shaft.