Nine-thirty in the evening.

Lu Yixin watched the time and took out her five-star high school chemistry problem book filled with difficult questions. The cover had been wrapped in a girlish pink book sleeve. She took a deep breath and turned to the folded page.

On Saturday nights at nine-thirty, the one on duty in the pharmacy was Zheng Fei. Fang Yongnian would not leave tHecheng on this day. At this hour, he would usually have finished dinner and showered — one of his rare evenings off.

Lu Yixin’s collection of abnormal, torturous problems was prepared precisely for such evenings of rest — of course, she could not use it every week. That would disturb Fang Yongnian’s rest.

Once every two or three weeks was the best rhythm.

She chose questions that even Zheng Ranran would need at least fifteen minutes to work through, marking them carefully with a star before putting them away. To have Fang Yongnian teach her such problems meant they would talk on the phone for over half an hour and if luck was with her and Fang Yongnian was in a good mood, they might even chat idly about everyday things.

Lu Yixin took another breath, snapped a picture of the problem with her phone, and sent it to Fang Yongnian on WeChat.

A minute later, she dialed his number.

The call didn’t connect right away. Lu Yixin listened to the ringing tone and bit her lip.

At this time of night, Fang Yongnian should be free. Why hadn’t he answered for so long?

Had he finally guessed her trick, and didn’t want to bother with her anymore?

Or perhaps, as her mother said over dinner today, Fang Yongnian was so busy, and her clinging to him so shamelessly was improper and rude.

Lu Yixin began to bite her nails in agitation.

Countless strange thoughts flashed through her mind. She even began to wonder — if her little trick was seen through, what excuse could she use next time to call him? These calls came only once every two or three weeks, lasting barely half an hour each time.

She had already been so careful.

Just as the line was about to play the “unanswered” tone, the call connected. Fang Yongnian’s voice came through — “Hello?” — and Lu Yixin’s eyes instantly turned red.

Maybe she was being a little neurotic. Lu Yixin rubbed her eyes, disgusted with herself.

“I…” She cleared her throat. “There’s a chemistry problem I don’t really understand.”

Fang Yongnian was silent for a moment, then mumbled, “Wait a bit.”

Lu Yixin sniffled again.

He was probably busy, she thought.

So he hadn’t seen her WeChat message yet.

The girl’s heart had just gone through a roller coaster ride. Now she held her phone close to her ear, afraid to miss a single sound from his end.

He should be at home, it was very quiet around him.

He lived in a gated community not far from her house, a very quiet place at night.

He seemed to be moving something; faint sounds of glass sliding on the floor could be heard from the other end. After two more minutes, he picked up the phone again. His voice was clearer than before as he said once more, “Wait a bit, let me look at the question.”

He… really was busy.

Lu Yixin, with her keen sense, caught a slight change in his tone. His voice sounded like he was suppressing his breath, the ends of his words short and somewhat hurried.

“Uncle Fang.”

This time, Lu Yixin truly felt uneasy. “This question isn’t that urgent. I can ask next time.”

She had disturbed him.

She had made that damn call at the very moment he least wanted to be disturbed.

There was again the sound of glass sliding against the floor from Fang Yongnian’s side. This time, Lu Yixin heard him take a sip of water.

“This question isn’t hard.” After that sip, his voice finally returned to normal. In the familiar tone she knew well, he asked, “Which part don’t you understand?”

She didn’t understand a single word of that question.

It had only ever been an excuse to call him, just like every other Saturday night at nine-thirty when she had “bothered” him. She would say she didn’t understand a single word, and Fang Yongnian would sigh and start explaining from the beginning, one line at a time.

Fang Yongnian explained questions very thoroughly. He was, in truth, a patient man. He had never lost his temper even when she failed to grasp the same concept after several repetitions.

At most, he would sigh into the phone and tell her to “use her brain” and listen again.

But tonight, she had disturbed him.

“I…” She suddenly couldn’t bring herself to act spoiled as usual, pretending not to understand. “I’ll just ask Ranran tomorrow. It’s not urgent.”

“Which part don’t you understand?” Fang Yongnian had already taken out pen and paper. “Let’s start from the beginning.”

The chemistry problems Lu Yixin asked were mostly beyond the curriculum for a second-year high school student. Each time he explained, he had to think of ways to simplify the problem to concepts she could understand. It took real mental effort.

But in his current state, having something to focus on was a good thing.

He didn’t notice Lu Yixin’s unease at all. Now that he finally had something to distract himself with, he forced all his attention onto the problem she had sent.

“The reaction between mixed acid and Cu should be solved using the ionic equation, not the chemical equation…” he began patiently from the most basic part, brows slightly furrowed, with cold sweat still un-wiped on his forehead.

Lu Yixin was quieter than ever before.

She no longer joked, no longer swooned over Fang Yongnian’s magnetic voice, no longer sighed over his intelligence, no longer imagined that she was special to him. After all, she had never seen him show such patience toward anyone else.

She held her pen and kept calculating. Every sentence he spoke, she memorized carefully.

This time, she even worked out the answer before he said it. The whole call lasted only ten minutes.

Fang Yongnian was taken aback. Ten minutes of focused explanation had successfully shifted his attention, and only then did he realize the girl was acting differently tonight.

“You’ve gotten smarter,” he said with a smile, leaning back in his chair and wiping the sweat from his forehead.

His voice now sounded completely normal.

Whether it was real or an act, she couldn’t tell.

“Is there… someone at your house?” Lu Yixin asked cautiously.

The tone in his voice when he had first answered the call, and the sound of glass dragging across the floor, still haunted her.

Fang Yongnian raised an eyebrow.

“I’m just a little worried,” Lu Yixin said even more carefully. “At a time like this, it’s probably better if there’s someone at home, right?”

Fang Yongnian was almost surprised. “How did you know?”

He had clearly said nothing on the phone earlier, and even the sound of him moving the mirror had been faint. How had this girl noticed?

“I guessed,” Lu Yixin said, finally letting out a breath.

Since Fang Yongnian didn’t hide it from her, it meant the episode wasn’t too serious.

“You really have gotten smarter,” Fang Yongnian said with a smile, his tone perfectly normal. “It’s fine. You called at just the right time.”

Lu Yixin completely relaxed, and her eyes reddened again.

“I thought…” she began foolishly, but before she could finish, tears started to fall.

She had thought she’d disturbed him, that she had picked the worst possible time to call. He had been having an episode. Everyone knew he had this condition, but he never told anyone when it acted up.

His pride was so strong that she’d feared her call would make him resent her.

And it wasn’t even a call for studying. It was just an excuse to find a difficult question, to bother him, to hear his voice. Every time after he explained a question, she could barely solve another one using the same concept.

She was, really, just being childish.

Yet he said her call had come at the right time.

Once tears started, it was hard to stop them. Lu Yixin rubbed at them clumsily while noisily flipping through her book. “I still have some other questions here…”

She had focused too hard earlier, finishing the question in less than ten minutes.

What a waste…

A call like this only came once every two or three weeks…

On the other end, Fang Yongnian couldn’t help but laugh and sigh as he listened to her crying and laughing at the same time. The sound of her sniffling, flipping through pages, muttering strange internet slang he couldn’t quite catch, all chattering and chaotic.

Lu Yixin’s emotions were always worn on her sleeve. This kind of sudden, inexplicable crying—he’d seen it countless times.

He never quite understood what exactly she was crying for each time, but he had long since grown used to her temperament that changed with the wind.

Leaning back in his chair, Fang Yongnian looked around. The kettle he’d knocked over during the sudden flare-up still lay on the floor. The house was a mess.

He listened to the lively rustle of Lu Yixin pulling out two more chemistry problems, both still impossibly difficult for a second-year student.

“What kind of book is that of yours?” he couldn’t help but ask, curious. Every problem she brought up was so strange, its knowledge point so obscure it might as well have come from the Arctic Ocean.

Lu Yixin chuckled on the other end, tears not yet dry but already sounding smug.

She didn’t cry again, but her reactions had slowed. He had to explain the same concept three times before she finally responded with an enlightened “Oh!”

Fang Yongnian gave a wry smile, switching his phone to the other ear, and warned, “Use your brain.”

The night had grown a little deep.

After hanging up, Fang Yongnian sat alone for a long time.

More than fifty percent of amputees suffer from a condition whose name sounds like a joke, yet is an unbearably cruel and persistent pain—phantom limb pain.

The sensation of the missing limb remains, along with pain or itching of varying intensity and nature.

That leg, clearly sawed off with a blade—that limb, clearly no longer his own—in some space that no longer exists, still felt pain as real as day.

It couldn’t be rubbed, touched, or seen. But it hurt, undeniably.

He had tried all sorts of methods—taken painkillers, undergone psychotherapy—but the pain still came without warning, impossible to defend against.

There was a triangular mirror in his home.

Whenever the phantom limb pain attacked, he would place the mirror between his legs, move his intact left leg, and, through the mirror, tell his brain that the other leg was still there.

Each time he used this ridiculous, almost laughable psychological compensation to ease the pain, the effect was minimal—but still, it helped a little.

Today, he had just taken out the mirror when his phone rang.

At first, he hadn’t wanted to answer it.

This kind of pain was far more irritable than ordinary pain. The right leg that no longer existed—by hurting this way again and again—kept reminding him that he was now an incomplete man, that his body was no longer whole.

He couldn’t even soothe his pain the way a normal person could. By simply rubbing it away.

He had wanted to throw that noisy phone into the corner. Yet when he picked it up and glanced at the caller ID, he ended up answering after all.

He had always known, Lu Yixin was different to him.

He had a special patience for her. He easily agreed to any of her requests. He even went soft when it came to her.

Zheng Fei had noticed, teasing him for being a pervert.

Perhaps he truly was, in a way.

At first, he had been good to that girl because she was easy to please. She liked the same food he did, had a good temper, wasn’t spoiled or noisy, just open-hearted and a bit silly.

She didn’t have any of those bratty traits most kids had. She looked carefree, but was actually thoughtful and sensible.

She was easy to get along with.

Later on…

She became the only person in his messy life who hadn’t changed.

He still missed those days. Those days when he had all his limbs, when life had goals, when everything was simple.

Lu Yixin was the last remaining trace of that time in his life.

He indulged her in a twisted sort of way, as though by indulging her, he could allow himself to remember those good, unbroken days.

“Quite clever…” Fang Yongnian murmured to himself. Finally, he stood, tossed the fallen kettle into the trash bin.

The stump no longer felt anything. Once gone, it was only emptiness.

He turned off the light, pulled the blanket over himself, and lay flat, staring at the ceiling.

“Really…” he murmured again in the darkness.

Tonight, it was indeed a good thing that the girl had called.

At least, all the pain hadn’t been for nothing.