Chapter 1

2, 15, 40, 77, 165, __

It was a sequence puzzle with a missing number.

It was also a top student’s dying message.

After answering the final question on his high school entrance examination math paper, the boy left that string of numbers on his answer sheet. Then he climbed out the window and threw himself to his death, putting a full stop to his own life.

It happened during the 2004 high school entrance examination, in the last subject of the exam: mathematics.

That year’s paper was so difficult that even the proctors were scratching their heads over the answers. In the entire room, only Chen Shouzhong—the perennial top student in his grade—looked calm. He filled every inch of his paper, including the last part of the final problem.

Half an hour before time was called, Chen Shouzhong suddenly dropped his pen, climbed through the classroom window, mounted the railing, and pitched forward in a diving motion.

Every student who saw it screamed.

Then came an uproar, the noise growing louder and more chaotic by the second.

Chen Shouzhong, the genius, had jumped from the building.

His skull shattered. He died on impact.

To make absolutely certain that he would die, he had folded both arms across his chest in midair so his head would strike the ground first. The surveillance cameras recorded everything.

I was a police officer. I had seen more crime scenes and surveillance footage than I cared to remember, yet that recording of Chen Shouzhong’s fall filled me with an inexplicable dread.

How could a ninth grader be so utterly determined to die?

How could he remain so calm in the last instant of his life?

Once I learned more about him, I immediately realized this case was different. It was nowhere near as simple as I had assumed.

Chen Shouzhong was one of heaven’s chosen. He had won first prize in the provincial Mathematical Olympiad, represented our province at the national competition, and placed in the top ten nationwide. His extraordinary gifts in science had already earned him provisional admission to No. 1 High School. The entrance examination was merely a formality for him.

After his death, the education authorities pulled his papers and graded them early. Chinese: 125 out of 150. Mathematics: 150 out of 150. English: 141 out of 150. Physics: 120 out of 120. Chemistry: 99 out of 100. Politics: 95 out of 100.

Those marks placed him among the top five students in the city, at the very least.

He could not possibly have killed himself because the exam had gone badly.

More baffling still, after completing the final math problem, he had written:

2, 15, 40, 77, 165, __

Those were the last symbols he ever left behind—the message he bequeathed to the world.

The sequence was plainly connected to his death. Through the education bureau, our criminal investigation unit sent it to the city’s mathematicians. Not one of those decorated experts could solve it.

The police demanded strict confidentiality, but in a small, remote city like ours, secrets leaked through every wall. A gifted teenager had achieved miraculous entrance-exam scores, then ended his life by jumping from a building, leaving a numerical riddle behind. It became the only thing people talked about over tea and dinner.

Speculation about his death grew stranger by the day. Some claimed an organized crime ring had forced students to cheat. Some said a perverted teacher had assaulted him. Others said he had been possessed by a ghost.

Then we found records showing that Chen Shouzhong had been treated for depression. He had been diagnosed with moderate depression before his death. We quickly closed the case as a suicide caused by depression, hoping to stop the public from inventing more rumors.

I thought that was the end of it.

I had no idea Chen Shouzhong’s death was only the opening move in a far larger conspiracy.

One month later, my son Zhong Qiu’s entrance-exam results came out. He had performed exceptionally well and, by some miracle, cleared the general high school cutoff. The boy had brought honor to the Zhong family.

I asked what reward he wanted. He said he wanted me to take him to the mall’s inflatable castle so he could relive the pleasures of childhood.

Every part of me hated the idea, but I took him anyway.

Then, in the time it took me to step outside and buy a pack of cigarettes, my son disappeared.

I searched every corner of the mall. There was no sign of him.

He had brought his Little Smart phone that day. I called again and again, but it remained switched off. I phoned my wife, Zhao Jing, and asked whether our son had gone home.

She was completely bewildered. “No. Isn’t he at the mall with you?”

A terrible premonition rose inside me.

The thing police officers fear most is an old enemy coming for the family. In nearly thirty years on the force, I had sent enough criminals to prison to fill a shipping container: murderers who dismembered bodies, kidnappers who killed their victims after collecting ransom, sadistic rapists, traffickers in human organs.

Their vicious faces flickered through my mind like an endless slide show. Cold sweat ran down my back.

I called my protégé Wang Guoqing and told him to bring the others at once. The men split into search teams while Wang Guoqing and I checked the surveillance footage.

A blurry black shape appeared on camera, slipping behind the inflatable castle when no one was looking.

The rear of the castle connected to the mall’s back entrance. In an alley nearby, we found Zhong Qiu’s snapped key chain, his Little Smart crushed under someone’s heel, and a length of steel scaffolding pipe. There were signs of a struggle all around it.

We sent the pipe to the evidence center for fingerprints. There were many, and we compared them one by one against our internal database.

One match came back almost immediately: Chen Zhenshi.

I remembered him well.

Four years earlier, he had been arrested for rape. I had led the interrogation. After leaving prison, he opened a scaffolding-rental shop in the neighboring county.

His son, Chen Shouzhong, had been Zhong Qiu’s classmate—the same boy who had jumped to his death during the entrance examination a month earlier.

There was no question that Chen Zhenshi was a prime suspect.

We summoned him at once.

He seemed prepared. He cooperated and followed us back to the station without complaint.

Under the rules, I was personally involved in the case and should have recused myself. By then, I no longer cared.

I exhausted every interrogation technique I knew, but Chen Zhenshi’s mouth might as well have been sealed with cement. No matter how I pressed him, he refused to speak.

Only half an hour remained before the twelve-hour limit on the summons expired. Criminal procedure law forbade us from holding him beyond that. In thirty minutes, we would have to let him walk.

I shot to my feet, switched off the recording equipment, and turned to Wang Guoqing.

“Go outside.”

He refused. He was afraid I would make a mistake.

The rage inside me finally burst free. “Get out! Get the hell out!”

He planted himself in the chair and would not move.

Then Chen Zhenshi finally spoke, his voice low and composed.

“Young man, go on outside. Officer Zhong and I need to have a proper talk.”

Soon, Chen Zhenshi and I were alone in the interrogation room.

“Officer Zhong. Long time no see.”

“What the hell do you want, Chen Zhenshi? Where have you hidden my son?”

“You care a great deal about your son, Officer Zhong. What about mine? Did you ever find out why Chen Shouzhong died?”

“I’ve already told you. He killed himself because of depression. The hospital provided the diagnosis of moderate depression and the records of his prescriptions. Do you think they were forged?”

“Even if he had depression, why did he have to kill himself in the examination room?”

For a moment, I had no answer.

When I remained silent, Chen Zhenshi stared into my eyes and enunciated every word.

“Do you honestly think a student of your son’s ability could have cleared the general high school cutoff?”

My heart clenched as though an invisible fist had closed around it. “What are you saying?” I ground the words through my teeth.

His expression turned sinister.

“You have a son. Can you imagine the shock and despair of watching him die before your eyes? Did you never wonder why a child who had nothing to fear from an examination would choose its final moments to kill himself? Shouldn’t someone pay for his death?”

We had initially considered whether bullying or some other juvenile offense lay behind the case. But the victim was dead, his parents had not pursued the matter, and we had chosen the path of least resistance.

We never imagined Chen Zhenshi had long since lost faith in us. He meant to conduct his own trial.

And my son was the one in the dock.

Twenty-five minutes remained.

Chen Zhenshi sat there with complete confidence. He had plainly calculated every step.

I took a deep breath, lit a Liqun cigarette, and held it between my lips. The nicotine slowly steadied me.

“Want one?” I asked.

He mimed smoking. I lit a cigarette, placed it between his lips, and said, “Tell me about the exam.”