Ban Xia found it hard to understand.

BG4MXH said this was a complex physics problem.

The word “physics” alone sounded complicated.

A complex physics problem meant complexity squared—Ban Xia knew, even thinking with her toes, that her toes couldn’t figure this out.

So she simply stopped thinking about it.

Better to let her toes rest comfortably in her slippers. They’d suffered enough from walking all day; making them think would be too cruel, wouldn’t it?

Time to wash her feet.

She crossed her legs, pulled off both socks, tied them together, and after taking quick aim, tossed them—direct hit on the headboard!

Ban Xia put on her slippers, pulled out the washbasin from under the bed, grabbed the bare towel from the hook behind the door, and then carried the basin to the dark living room for hot water.

In October, when the weather was still properly hot, washing up didn’t require much hot water.

She went to the bathroom next, scooped up several ladles of clean water, and carried the half-full basin back to her room. The girl first set the basin on the floor, then plopped down on the edge of the bed.

She reached up to feel her hair, rubbing and sniffing it. Could it produce enough oil to braise eggplants?

No.

Good, then no hair washing tonight.

Ban Xia used a hair tie to gather her hair at the back of her head in a bun, like a ballet dancer exposing her slender neck, then bent down to fetch the towel, wrung it out, and washed her face.

Ban Xia’s skin was very fair, fair enough to make her teacher envious.

The teacher would often pinch her face, stare at it for a while, then ask, “Girl, how do you never tan?”

The girl wiped her body in front of the electric fan, feeling delightfully cool as the breeze hit her clean skin.

She pulled at her nightgown’s collar, letting the wind blow inside.

Finally, washing her feet, Ban Xia soaked both feet in the water, leaning down to massage them slowly.

She kneaded from her knees down to her toes, then circled from tiptoes to heel. While her foot tops and toes remained soft and fair, her soles had developed a rough callus. In this world without other transportation, Ban Xia could only rely on her bicycle and legs to get around. Back when her teacher was still here, she would often kneel in front of Ban Xia to massage her feet. The teacher’s fingers were long and skilled, pressing firmly from sole to calf, helping her stretch ligaments and relax muscles until the young girl’s feet turned red from the hot water.

The teacher always said that in this world, humans survive on their feet.

How wonderful it was to have feet that could run and jump.

Ban Xia had seen her teacher remove one of her own feet, then lean against the wall tinkering with it.

That lower leg had no muscle, no blood vessels, no skin or bone—it was a frame made of metal and plastic. The teacher called it a prosthetic.

Where had the teacher’s original foot gone?

She said it had been vaporized.

Despite having one artificial foot, the teacher remained agile. Ban Xia had never met anyone as capable as her teacher—and wasn’t she quite young too?

Ban Xia fell back onto the bed, grabbing the plastic desk lamp from the headboard.

She turned on the lamp and closed her eyes. The faint light penetrated her eyelids into her pupils, landing on her retinas. In the darkness, Ban Xia saw a dark red circle.

She knew this was the color of light passing through blood vessels. Opening her eyes, the bright LED light pierced them, making Ban Xia instinctively squint. The dark red circle became a white halo.

Closing her eyes again, the afterimage lingered on her retinas. The halo remained but gradually dispersed. She opened her eyes once more, and the light shot directly into her pupils again.

Ban Xia repeatedly opened and closed her eyes. The edge of the dark red circle projected on her retina gradually became clearer. It rolled and flickered before her eyes, finally breaking free from the dark background to become a red eyeball.

Ban Xia’s eyes snapped open as she touched her forehead.

It was slightly sweaty, though she wasn’t sure if it was from the heat.

BG4MXH said he needed to understand the cause of all this—it was key to their mission. Only by understanding why the world had been destroyed could they work together to pull the world back from the brink of destruction.

Was this possible?

BG4MXH said it was because humans of that era possessed tremendous power.

But in the girl’s eyes, hadn’t that powerful human civilization been destroyed anyway? Ban Xia’s world and BG4MXH’s were the same, just in different eras. If humanity hadn’t been destroyed, she wouldn’t be surviving here alone.

Ban Xia didn’t know the true reason for the world’s destruction. If she knew, she would have told BG4MXH already. Surely someone in this world once knew how it was destroyed, but they were all gone now. Ban Xia had only hazy memories of the apocalyptic era. Could BG4MXH uncover the truth of the apocalypse with just these vague memories?

Ban Xia pondered silently, lazily lifting her calf and then letting it fall, gently striking the water’s surface.

“Splash!” Her foot met the water, sending up a string of droplets as it rose.

Was all this effort truly meaningful?

Could history that had already happened be changed?

BG4MXH himself was already dead, having perished in the turmoil and disasters of the past twenty years. All his family, friends, and those he relied on had died in those two decades of chaos and catastrophe. Ban Xia was essentially talking to a ghost, conversing with a specter that lingered in the electromagnetic world.

Could ghosts and specters change their fate?

If they really could change the future, alter the history they’d witnessed, and save humanity from destruction, what would this world become?

Would it instantly transform back into bustling, crowded cities full of life?

What would become of her?

Would she still exist?

Would the Ban Xia who loved singing, excelled at archery, could catch fish and cook—yet still lived such a hard life—still exist?

Would everything she’d experienced, all her memories, vanish in an instant?

Would the person lying here become a different Ban Xia?

The girl pondered silently.

In BG4MXH’s words, this was a complex physics problem.

Ban Xia thought with her toes, knowing full well her toes couldn’t figure it out.

But the world on the other end of the radio signal had 6.5 billion people. Let them think about this problem. With such an unimaginably large number of people, Ban Xia believed heroes capable of saving the world would emerge. She lay languorously on her bed, tilting her head to look at the wooden frame on the windowsill. Inside the frame was a dim green fluorescence and a small picture: an old comrade holding lightning, splitting open an iron warship with a single strike.

Who was that person?

Someone that powerful should be able to save the world, right?