Cheng Xin mourned Vadimov, who had cared for her like a big brother and helped her adjust to life in a foreign country. She missed his generosity most of all. Though Cheng Xin had attracted notice with her intelligence and seemed to shine brighter than Vadimov -- despite the fact that she was supposed to be his aide -- he had never shown any jealousy. He had always encouraged her to display her brilliance on bigger and bigger stages.

Within the PIA, there were two types of reaction to Vadimov's death. Most of the technical staff, like Cheng Xin, grieved for their boss. The intelligence specialists, on the other hand, appeared more displeased by the fact that Vadimov's body had not been retrieved in time, rendering his brain unusable.

Mikhail Vadimov died. While crossing the Harlem River on I-95, his car slammed through the guardrails on the Alexander Hamilton Bridge and plunged into the water below. It took more than a day before the car could be retrieved. An autopsy revealed that Vadimov had been suffering from leukemia; the accident was the result of retinal hemorrhages.

She consulted medical specialists and learned that it was possible to intentionally induce leukemia. All you had to do was to place the victim in an environment with sufficient radiation. But getting the timing and dosage right was no trivial matter. Too little would not induce the illness in time, but too much would kill the victim with radiation sickness, possibly damaging the brain. Timing-wise, based on the advanced state of Vadimov's illness, the scheme against him would have to have begun right around the time the PDC started to promote euthanasia laws around the world. If there was a killer, he was extremely skilled.

Gradually, a suspicion grew in Cheng Xin's mind. It seemed like too much of a coincidence. She shuddered the first time the idea surfaced in her mind -- it was too frightening, too despicable to be endured.

Secretly, Cheng Xin swept Vadimov's office and apartment with a Geiger counter, but discovered nothing unusual. She saw the picture of Vadimov's family he kept under his pillow: His wife was a ballerina eleven years younger than him, and their little daughter… Cheng Xin wiped her eyes.

Vadimov had once told Cheng Xin that, superstitiously, he never left family photos on desks or nightstands. Doing so seemed to him to expose them to danger. He kept the pictures hidden and only took them out when he wanted to look at them.

Since meeting Tianming back in China, Cheng Xin's heart had grown heavier over time, until she sank into a depression. She recalled the first time they met. It was just after the start of their first semester in college, and all the aerospace engineering students took turns introducing themselves. She saw Tianming sitting by himself in a corner. From the moment she saw him, she understood his vulnerability and loneliness. She had met other boys who were isolated and forlorn, but she had never felt like this: as though she had stolen into his heart and could see his secrets.

Every time Cheng Xin thought of Vadimov, she also thought of Yun Tianming. Tianming and six other candidates had been moved to a secret base near PIA Headquarters to undergo a final series of tests, after which one of them would be picked.

One night, Cheng Xin had another nightmare. She was again at her star, but the red sea algae had turned black. Then the star collapsed into a black hole, a lightless absence in the universe. Around the black hole, a tiny, glowing object moved. Trapped by the gravity of the black hole, the object would never be able to escape: It was a frozen brain.

Cheng Xin woke up and looked at the glow of New York's lights against her curtain. She understood what she had done.

Cheng Xin liked confident, optimistic boys, boys who were like sunlight, warming themselves as well as the girls with them. Tianming was the very opposite of her type. But she always had a desire to take care of him. In their interactions she was careful, fearful of hurting him, even if unintentionally. She had never been so protective of other boys.

When her friend had come to New York and Tianming's name came up, Cheng Xin discovered that although she had tucked him away in a distant corner of her memory, his image was surprisingly clear when she recalled him.

She had done nothing that she ought to be ashamed of, nothing that should trouble her conscience.

The next day, Cheng Xin went to see Wade.

From one perspective, she had simply passed along the PIA's request; he could have said no. She had recommended him because she was trying to protect the Earth and its civilization, and his life had almost reached its end -- had she not arrived in time, he would be dead. In a way, she had saved him!

But she also understood that this was how someone could sell their mother to a whorehouse.

As usual, Wade stared at his lit cigar in his office. She rarely saw him perform the tasks that she associated with conventional administration: making phone calls, reading documents, attending meetings, and so forth. She didn't know when, if ever, Wade did these things. All she could see was him sitting, deep in thought, always deep in thought.

Cheng Xin thought about hibernation. The technology was mature enough that some people -- mostly terminally ill patients seeking a cure in the future -- had already entered the long sleep. Tianming had a chance. Given his social status, it would be hard for him to afford hibernation, but she could help him. It was a possibility, an opportunity that she had taken from him.

Wade's comment stunned Cheng Xin and chilled her heart. One of the first tests they conducted was to put each candidate under a special form of general anesthesia that caused the person to lose feeling in all parts of the body and sensory organs but remain conscious. The experience was intended to simulate the conditions of a brain existing independent of the body. Then the examiners assessed the candidate's psychological ability to adapt to alien conditions. Of course, since the test designers knew nothing about conditions within the Trisolaran Fleet, they had to fill out their simulation with guesses. Overall, the test was quite harsh.

"Why? He has scored the best in our tests."

Cheng Xin explained that she thought Candidate #5 was unsuitable. She wanted to withdraw her recommendation and ask that the man be removed from consideration.

"But he has only an undergraduate degree," Cheng Xin said.

"You certainly have more degrees," said Wade. "But if we used your brain for this mission, it would, without a doubt, be one of the worst brains we could have chosen."

"That is precisely Candidate #5's best quality! You're talking about human society. Someone who feels comfortable with this environment has also learned to rely on it. Once one is cut off from the rest of humanity and finds oneself in a strange environment, one is very likely to suffer a fatal breakdown. You're a perfect example of what I'm talking about."

"He's a loner! I've never seen anyone so withdrawn. He doesn't have any ability to adjust and adapt to the conditions around him."

Cheng Xin had to admit that Wade's logic was sound. She probably would suffer a breakdown from the simulation alone.

She certainly knew that she had no clout to get the top administrator of the PIA to give up on a candidate for the Staircase Program. But she didn't want to give up. She steeled herself. She would say whatever was necessary to save Tianming.

"He's made no meaningful attachments in life. He has no sense of responsibility to humanity, or love." After saying this, Cheng Xin wondered if there was some truth to it.

Cheng Xin had indeed seen this in Tianming's background file -- so she did know someone really rich, after all. But she didn't believe for a minute that Hu Wen was the one who had given her the star. The very idea was ridiculous. If he liked her, he would buy her a fancy car or a diamond necklace, not a star.

"Oh, there is definitely something on Earth he's attached to." Wade's gaze remained on the cigar, but Cheng Xin could feel his attention being deflected from the cigar's lit tip onto her, carrying with it some of the flame's heat. To her relief, Wade abruptly changed the subject.

"I had thought none of the candidates were anywhere near being suitable, and I was running out of ideas. But you've reaffirmed my faith in #5. Thank you."

"Another excellent quality of Candidate #5 is his creativity. This makes up for his lack of technical knowledge. Did you know that an idea of his made one of your classmates into a billionaire?"

Wade finally lifted his eyes to look at Cheng Xin with his cold, predatory smile. As before, he seemed to take pleasure in her despair and pain.

The ceremony took place in the UN General Assembly Hall. Unlike the session announcing the Wallfacer Project a few months ago, this ceremony was closed to the public. Besides the seven Staircase Program candidates, the only attendees were Secretary General Say, the PDC rotating chair, and a few observers -- including Cheng Xin and other members of the PIA working on the Staircase Program -- who filled the first two rows of seats.

But Cheng Xin didn't lose all hope. She was attending the Oath of Allegiance Ceremony for Staircase Program candidates. According to the Space Convention, as amended post-Crisis, any person using resources of the Earth to leave the Solar System for economic development, emigration, scientific research, or other purposes must first take an oath pledging loyalty to humanity. Everyone had thought this provision would not be invoked until far in the future.

The ceremony didn't take long. In turn, each candidate put his or her hand on the UN flag held up by Secretary General Say and recited the required oath to be "loyal to the human race for all time, and to never perform any act that harms humanity's well-being."

Four candidates were lined up before Yun Tianming -- two Americans, a Russian, and a British man -- and two more stood behind him: another American, and another Chinese. All the candidates looked sickly, and two had to use wheelchairs. But all looked to be in good spirits -- not unlike oil lamps giving off a final burst of light before burning out.

Cheng Xin looked at Tianming. Since the last time she had seen him, he looked thinner and more pallid, but appeared very calm. He didn't look back in her direction.

It was Tianming's turn. Though Cheng Xin was an atheist, at that moment she wished she could grab the Bible from that man and pray to it: Tianming, please take the oath, please! I know you're a responsible man. You'll be faithful to the human race. Like Wade said, there are things here that you cannot bear to part with…

The first four candidates' oaths went off without a hitch. One of the Americans, a physicist in his fifties with pancreatic cancer, struggled up from his wheelchair and climbed onto the rostrum by himself. The candidates' voices echoed in the empty hall, frail but full of dedication. The only interruption in the routine was the British man asking whether he would be allowed to take his oath on a Bible. His request was granted.

Tianming picked up the blue UN flag from Say and lightly draped it on the lectern next to him.

She didn't hear him repeat the oath.

She watched as Tianming mounted the dais, watched as he walked in front of Secretary General Say, and then squeezed her eyes shut.

"I want to see another world. As for whether I'll be faithful to humanity, it will depend on what kind of civilization I see among the Trisolarans."

"I will not take the oath. In this world, I feel like a stranger. I've never experienced much joy or happiness, and didn't receive much love. Of course, these can all be attributed to my faults --"

"-- but I will not take this oath. I do not affirm any responsibility to the human race."

His tone was placid, as though he was reviewing his own life. Cheng Xin, sitting below the dais, began to tremble as though waiting for an apocalyptic judgment.

Say nodded. "Your oath is entirely voluntary. You may go. Next candidate, please."

"Then why have you agreed to be in the Staircase Program?" asked Say. Her voice was gentle, as were her eyes on Tianming.

Tianming had passed the final test.

This is a fun game, isn't it?

Cheng Xin shook as though she had fallen into an ice cellar. She bit her bottom lip and forced herself not to cry.

Wade, who was sitting in the front row, turned around to look at Cheng Xin. He took delight in even more despair and pain. His eyes seemed to speak to Cheng Xin. Now you see what he's made of. But… what if he's telling the truth? If even we believe him, the enemy will believe him, too.

Wade turned back to the rostrum, then seemed to remember something vital, and glanced back at Cheng Xin again.

Tianming's unexpected refusal seemed to change the atmosphere in the hall. The last candidate, a forty-three-year-old HIV-positive American NASA engineer named Joyner, also refused to take the oath. She explained that she had not wanted to be here, but she had felt compelled to come because she believed that if she refused, her friends and family would despise her and leave her to die alone. No one knew if she was telling the truth or if Tianming had inspired her.

The moment had arrived. Cheng Xin was informed that Tianming's condition had suddenly deteriorated. They needed to remove his brain right away. The procedure would be conducted at Westchester Medical Center.

The next night, Joyner's condition suddenly deteriorated. An infection that turned into pneumonia caused her to stop breathing, and she died before dawn. The medical staff did not have enough time to remove her brain for flash freezing, and it was unusable.

Cheng Xin stood frozen. Everything seemed to transform around her. What she had seen before were mere shadows; only now did life's true colors reveal themselves. The tidal wave of emotion made her stumble, as if the ground had disappeared.

Cheng Xin hesitated outside the hospital. She didn't dare enter, but she couldn't bear to leave. All she could do was to suffer. Wade, who had come with her, walked ahead toward the hospital entrance alone. He stopped, turned around, and admired her pain. Then, satisfied, he delivered the final blow. "Oh, I have another surprise for you: He gave you the star."

Tianming was chosen to carry out the mission of the Staircase Program.

A group of men and women in white coats turned around. The body had already been removed from the room. In the middle was a workbench, on top of which sat a cylindrical stainless steel insulating container, about a meter tall. It had just been sealed, and the white fog produced by the liquid helium still hadn't completely dissipated. Slowly, the white fog rolled down the surface of the container, flowed across the workbench, cascaded over the edge like a miniature waterfall, and pooled on the floor, where it finally broke apart. In the fog, the container appeared otherworldly.

She rushed into the hospital and dashed through the long, winding hallways until two guards outside the neurosurgery area stopped her. She struggled against them, but they held fast. She fumbled for her ID, waved it at them, and then continued her mad run toward the operating room. The crowd outside, surprised, parted for her. She slammed through the doors with glowing red lights over them.

Cheng Xin threw herself at the workbench. Her motion broke up the white fog, and she felt herself enveloped in a pocket of cold air that dissipated in a moment. It was as if she had briefly touched what she was seeking before losing it to another time, another place, forever.

She was too late.

She didn't know how much time passed before she felt the hand placed against her shoulders. Maybe the hand had been there for a long time, and maybe the owner of the hand had been speaking for a long time, as well.

Still wracked by sobs, Cheng Xin could not catch her breath, but what the voice said next got her attention.

"There is hope." It was the voice of an old man, gentle and slow. "There is hope."

"Think! If they can revive that brain, what would be the ideal container for it?"

Prostrate in front of the container of liquid helium, Cheng Xin sobbed. Her sorrow filled the operating room, overflowed the hospital building, flooded New York City. Above her, the sorrow became a lake, then an ocean. At its bottom, she felt close to drowning.

The voice did not offer empty platitudes, but a concrete idea.

She lifted her head, and through tear-blurred eyes, she recognized the white-haired old man: the world's foremost brain surgeon, affiliated with Harvard Medical School. He had been the lead surgeon during the operation.

Cheng Xin stared at the stainless steel container. Tears rolled down her face, but she didn't care. Then she recovered and stunned everyone: "What is he going to eat?"

"It would be the body that had carried this brain in the first place. Every cell in the brain contains all the genetic information necessary to reconstruct his body. They could clone him and implant the brain, and in this way, he would be whole again."

She sprinted out of the room, in as much of a rush as when she had barged in.

"I request that these seeds be included in the Staircase capsule."

Wade opened the envelope and emptied its contents onto the desk: more than a dozen small packets. He ticked through them with interest: "Wheat, corn, potatoes, and these are… some vegetables, right? Hmmm, is this chili pepper?"

The next day, Cheng Xin returned to Wade's office and deposited an envelope on his desk. She looked as pale as some terminally ill patients.

Wade put all the packets back into the envelope and pushed it across the desk. "No."

Cheng Xin nodded. "One of his favorites."

"But it's not, is it? Adding this weight would lead to a slower final cruising speed for the spacecraft, and delay the encounter with the Trisolaran Fleet by many years." That cold smirk again appeared on Wade's face. "Besides, he's just a brain now -- no mouth, no stomach. What would be the point? Don't believe that fairy tale about cloning. They'll just put the brain in a nice incubator and keep it alive."

Cheng Xin wanted to rip the cigar out of Wade's hand and put it out against his face. But she controlled herself. "I will bypass you and make the request to those with more authority."

"Just pretend his brain is eighteen grams heavier!"

"Why? These weigh only eighteen grams in total."

"I won't allow it. You're still useful to the PIA."

Cheng Xin turned around and started to walk away.

"We must make every effort to remove even point one eight grams of excess mass."

"It won't work. Then?"

"Then I'll resign."

Cheng Xin laughed bitterly. "You can't stop me. You've never been my real boss."

"You will not do anything I don't allow."

"The Staircase Program needs to send someone who knows Yun Tianming to the future."

"However, that person must be a member of the PIA and under my command. Are you interested? Or do you want to hand in your resignation now?"

"I agree to go to the future," Cheng Xin said. She leaned against the doorframe for support. She didn't turn around.

Cheng Xin stopped.

The only time Cheng Xin got to see the Staircase spacecraft was when its radiation sail unfolded in orbit. The giant sail, twenty-five square kilometers in area, briefly reflected sunlight onto the Earth. Cheng Xin was already in Shanghai, and she saw an orange-red glowing spot appear in the pitch-black sky, gradually fading. Five minutes later, it was gone, like an eye that materialized out of nowhere to look at the Earth and then slowly shut its eyelid. The craft's journey as it accelerated out of the Solar System was not visible to the naked eye.

Cheng Xin continued walking, but her stride slowed down. Finally, she stopped a second time. Wade's voice came again. "You'd better be sure about your choice this time."

Cheng Xin was comforted by the fact that the seeds did accompany Tianming -- not her seeds, exactly, but seeds that had been carefully selected by the space agricultural department.

The giant sail's mass was 9.3 kilograms. Four five-hundred-kilometer cables connected it to the space capsule, whose diameter was only forty-five centimeters. A layer of ablative material covered the capsule, making its launch mass 850 grams. After the acceleration leg, the capsule mass would be reduced to 510 grams.

The acceleration leg stretched from the Earth to the orbit of Jupiter. A total of 1,004 nuclear bombs were distributed along the route, two-thirds of which were fission bombs, the rest fusion. They were like a row of mines that the Staircase craft triggered as it passed by. Numerous probes were also distributed along the route to monitor the craft's heading and speed and coordinate minute adjustments to the positions of the remaining bombs. Like the pulses of a heart, successive nuclear detonations lit up the space behind the sail with blinding glows, and a storm of radiation propelled this feather forward. By the time the spacecraft approached Jupiter's orbit and the 997th nuclear bomb exploded, monitoring probes showed that it had achieved 1 percent of lightspeed.

As time passed, the spacecraft's trajectory would deviate farther and farther from the projection. Hopes that it would intercept the Trisolaran Fleet diminished. Based on its approximate final heading, it should pass by another star in six thousand years and depart the Milky Way in five million years.

There was no real reason to send Cheng Xin to the future anymore, but the PIA still asked her to enter suspended animation. Her mission now was to act as a liaison to the Staircase Program in the future. If this pioneering effort was to be helpful to humanity's spaceflight efforts in two centuries, someone who understood it deeply had to be there to explain the dead data and interpret the mute documents. Of course, perhaps the real reason for sending her was only one of vanity, a wish that the Staircase Program would not be forgotten by the future. Other large contemporary engineering projects had made similar efforts to send liaisons to the future for similar reasons.

That was when the accident occurred. Analysis of the frequency spectrum of the light reflected from the radiation sail showed that the sail had begun to curl, possibly because one of the towing cables had broken. However, the 998th nuclear bomb detonated before adjustments could be made, and the craft deviated from the projected course. As the sail continued to curl, its radar profile rapidly shrank, and it disappeared from the monitoring system. Without precise parameters for its trajectory, it would never be found again.

At least the Staircase Program was a half success. For the first time, a man-made object had been accelerated to quasi-relativistic speeds.

If the future wished to pass judgment on our struggles, then at least it was now possible to send someone to the future to explain the misunderstandings brought about by the passage of time.

As Cheng Xin's consciousness faded in the cold, she held on to a ray of comfort: Like Tianming, she would drift through an endless abyss for centuries.