Chapter 1: All The Variables
At 4:17 in the afternoon, the ventilation system stopped.
Qiao Zhiyi heard the fan grind once above them. The thin metallic whine stretched for 2.8 seconds before ending with a hard clunk.
Then there was nothing.
No hum of machinery. No labored rattle from the failing compressor. No whisper of air moving through the shelter’s narrow vents.
Only Pei Hanchuan’s breathing and the steady drip of condensation falling from the pipe above her head.
Zhiyi stared at the vent.
The temperature inside the shelter was already forty-eight degrees Celsius.
Outside, it was sixty-seven.
The concrete walls would delay the increase, but they couldn’t prevent it. Without ventilation, carbon dioxide would accumulate. The battery-powered fans would move air without cooling it. The remaining ice would melt within seventy-three minutes, perhaps less. They had 1.6 liters of water between them.
The next viable shelter was eleven kilometers away.
Under ordinary conditions, Zhiyi could walk that distance in two hours and twelve minutes.
These weren’t ordinary conditions.
The roads had softened beneath the heat. The air burned their lungs. There was no shade for nearly four kilometers, and Pei couldn’t walk.
She could pull him.
Their cart had lost its rear wheel three days ago.
She could repair it.
But they didn’t have the necessary parts.
She could build a drag sled from the cot frames.
But the metal would absorb too much heat. The friction would slow them. Pei weighed eighty-seven kilograms after years of food shortages. Their supplies added another twenty-three. She would collapse before they reached the first kilometer.
She could leave him and return with help.
There was no one left to help.
She could—
"Zhiyi." Pei’s voice came from behind her, but she ignored it as she continued to stare at the vent.
If she removed the filter, airflow might improve.
There was no airflow to improve.
If she opened the outer door—
The temperature would rise too quickly.
If they moved into the storage alcove—
Smaller space. Less thermal mass. Faster carbon-dioxide accumulation.
If they wet their clothes—
Not enough water.
If they—
"Zhiyi." She heard him. Understanding the sound wasn’t the problem. Stopping her thoughts while they were demanding all her focus was. She simply hadn’t reached the end yet. When she did, she would turn to him.
After all, there had to be an end.
Every problem had one. A correct sequence of actions existed whether she could see it immediately or not. Variables could be isolated. Risks could be ranked. Resources could be reassigned.
Seven years ago, Pei had survived because she needed shelter and he needed food.
Six years ago, they had survived the poisoned reservoirs because she calculated the contamination radius before either of them drank.
Four years ago, they had crossed the eastern ice sheet after she identified the buildings most likely to remain standing beneath the accumulated weight.
Last year, when the heat returned, they had moved underground before the roads melted.
The outcome was supposed to be survival. This wasn’t the optimal outcome.
Taking in a deep breath, her mind returned to the beginning and started again.
One failed ventilation system.
Two people.
One unable to walk.
Eleven kilometers.
Sixty-seven degrees outside.
No transport.
No assistance.
Insufficient water.
No viable route.
No viable route.
No viable route.
"Left hand," Pei said, his voice even... not even a hit of frustration.
Her fingers twitched, obeying his command before her brain even managed to catch up to his words.
"Open it."
Zhiyi looked down.
Her left hand was curled so tightly that her nails had cut four crescents into her palm. She watched her fingers slowly straighten. Blood gleamed against her skin before the heat began drying it.
"Good," Pei murmured. "Now turn around."
Like she was the robot everyone at school called her, she turned.
Pei Hanchuan was lying on the floor beside the lower cot. He had pulled himself out of his chair when the temperature began climbing, choosing the concrete because it was still marginally cooler than the air.
His useless legs rested at an unnatural angle beneath him.
He must have tried to reach her.
There was blood on one elbow where the skin had scraped away, and the old scars across his hands had gone white around his knuckles. Sweat soaked through his shirt, but his face was dry.
That was bad.
Dry skin in extreme heat indicated that his body could no longer regulate its temperature. His pulse would be rapid. His blood pressure would fall. Confusion would follow, then organ damage—
"Come here," he said, but Zhiyi didn’t move. She couldn’t. Her mind wasn’t under her control.
The distance between them was 2.3 meters.
Crossing it would require five steps.
That wasn’t a solution.
"Hanchuan, the ventilation system has failed," she said at last, her voice almost dreamy.
"I know," he replied, so soothing. She could listen to him speaking all the time.
"The internal temperature will exceed fifty degrees within approximately thirty-four minutes," she replied instead.
"I know."
"We can’t remain here."
"I know," he smiled back like this was a normal conversation.
"The western emergency shelter may still be functional, but without transportation—" Zhiyi continued, flicking her long black hair over her shoulder.
"We’re not going west."
"We have to," she insisted. The variables were telling her that that was the only way. There was no other possibility... other than...
"The road is exposed," he pointed out like she wasn’t the one who told him that.
"I know."
"You’ll die here." The moment the words past her lips, she felt herself choking on nothing. There was something stuck in her throat that she couldn’t swallow around. What could it be? She hadn’t eaten anything in days so it couldn’t be food.
What was the thing in her throat, and why was it causing her eyes to water?
Pei Hanchuan’s expression changed, though Zhiyi couldn’t identify how her her blurry vision. Impatiently, she wiped at her eyes.
His mouth curved, but it wasn’t a smile. Smiles were supposed to indicate happiness. There was nothing inside the shelter capable of producing that response.
"So will you," he said at last.