Spying

04 Sudoku

Before becoming colleagues, Ren Shaobai had seen Lan Youyin twice. The first time was from a distance. Back then, he hadn’t yet realized he had a nearsightedness problem, assuming the world everyone saw was as hazy and indistinct as his own. Even so, he had no doubt that Lan Youyin was beautiful.

For one thing, beauty isn’t just about the fine details of eyes or nose—it’s also about posture and aura. Lan Youyin carried herself with effortless grace, standing there with a natural elegance that drew the eye. For another, she was playing the lead role in a school play on stage. Surely the heroine couldn’t be an unattractive girl, could she?

Ren Shaobai, barely out of his teenage years at the time, was surrounded by plenty of girls. Naturally, the ones he remembered were the good-looking ones. After all, everyone appreciates beauty—he wasn’t about to hypocritically deny that.

The second time he saw her, they were much closer. Aside from confirming that her features were indeed flawless, he realized something else: how shallow his first impression of Lan Youyin had been years ago.

That day, he was troubled by something that later seemed trivial. Sitting in the back of a bus, he idly worked on a Sudoku puzzle, only to get stuck at the fifth box—numbers weren’t his strong suit, but his math-major roommate had insisted that solving these puzzles could sharpen the mind.

Just then, he noticed Lan Youyin standing in front of him, curiously eyeing his notebook. When she realized she’d been caught, she spoke up, slightly embarrassed: "This Sudoku isn’t like the ones in the newspapers."

Ren Shaobai explained that it was a modified version his math-major classmates had devised, tweaking some rules to make it more challenging. He then pointed to the parts he’d filled in to verify his reasoning, but she interrupted him halfway.

"The 1 here is wrong." Lan Youyin’s finger landed on the fourth box, then slid to the first. "That would mess up the 5 and 6 here because this column would end up with two 8s. The 1 should go here, and then this column’s two empty cells should be 4 and 7..."

The bus swayed gently, and the afternoon sunlight flickered across the back of her hand, shifting between light and shadow. Ren Shaobai’s gaze, however, lingered on her face, settling on the lashes that dipped slightly as she looked down. Only when she finished solving all nine boxes in one breath did he hurriedly look away, spotting the rolled-up newspaper in her hand—just enough to catch the date.

It was April 30, 1939.

At the Huaxiba stop, Lan Youyin got off the bus and walked away with a classmate she’d met at the station. For a fleeting moment, Ren Shaobai wanted to jump off and follow her—if not for the more pressing matter at hand.

But in those chaotic times, encounters between people were like the unique numbers in a Sudoku column—never to be repeated.

Lan Youyin also remembered that encounter, though not with Ren Shaobai, but with mathematics. This wasn’t to say she’d never studied math before—on the contrary, she had an excellent intuition for numbers. But that afternoon, she suddenly realized that mathematics wasn’t just about practical calculations in life; it could also point to something far more abstract.She accurately memorized the Sudoku puzzle in Ren Shaobai's hand because it was more challenging than those found in newspapers, with special constraints. Later, she imitated the style, creating and solving her own puzzles. One day, a schoolteacher noticed and suggested that if she was interested in mathematics, she could audit first-year math courses at the university.

In better times, this might have led the girl, who never imagined studying math, down an uncharted path—a story of following one's heart, inspiring future generations. But reality was different. Soon enough, Lan Youyin realized she couldn’t pursue pure mathematics—it was an abstract world, and she had far too concrete a mission to devote herself to.

Yet math still helped her. Years later, she passed an exam and secured a government job—working as a computational clerk at the Sino-American Cooperative Organization in Chongqing.

In the 30th year of the Republic, the Pacific War broke out. The Americans, eager to avenge Pearl Harbor and redeem themselves for earlier intelligence failures, launched a code-breaking project called "Magic," establishing branches worldwide to gather intelligence capable of cracking Japan’s supposedly "unbreakable" Purple Code. The Sino-American Cooperative Organization in Chongqing took on part of this work.

Of course, ordinary clerks like Lan Youyin had no idea they were part of a much larger scheme.

Assigned to the telecommunications unit, she processed massive daily calculations without knowing their purpose. But periodically, she would use newly acquired formulas to deduce whether her previous results matched what the higher-ups wanted. Most of the time, they didn’t.

One day, while waiting in the cafeteria line, another clerk voiced the same curiosity—what exactly were they doing? Lan Youyin hesitated but finally shared her guess: "It’s like we’re solving two kinds of Sudoku at once. One is man-made, with standard rules. The other seems randomly generated, with no known rules."

Her colleague was baffled, but a passing officer stopped and turned to look at her. Soon after, Lan Youyin was transferred to the decryption team.

Only then did she learn about the plan to crack the Japanese naval codes. Codes—the metaphysical world she had once pondered.

The other decryption team members were either university graduates with formal math training or early linguists of the era. In comparison, Lan Youyin’s knowledge of cryptography was that of a first-grader. Yet this didn’t stop the team leader from recognizing her untapped potential. If she could deduce objectives from chaotic calculations, perhaps she could also find a key within the even more chaotic codes.

However, just as Lan Youyin was being taught the basics of cryptography, news arrived from the Pacific front—the Americans had killed Yamamoto Isoroku, the mastermind behind the Pearl Harbor attack. The Japanese admiral’s precise itinerary had been uncovered through decrypted Purple Code messages.While the head of the decryption team breathed a sigh of relief, Lan Youyin felt a faint trace of regret. Of course, she didn’t believe her rudimentary knowledge of cryptography could outpace the Americans in cracking that cipher. She simply thought there ought to be some ambition rooted in mathematics itself. The team leader understood her thoughts and gave her the knowing look of a seasoned veteran observing an eager novice.

Lan Youyin did work as a decoder for some time, assisting in deciphering ciphered intelligence from the Japanese Foreign Ministry. On the eve of the war's end, she was even promoted to captain for decrypting what appeared to be weather reports, revealing the Japanese army’s retreat routes in India and Burma.

But that was all.

In 1946, the Nationalist government returned to Nanjing. The Sino-American Institute disbanded, and military institutions were reorganized. Lan Youyin had the opportunity to continue working in telecommunications decryption at the Second Department of the Ministry of National Defense, but she declined—for a reason.

"Oh right, Battalion Commander Qiao is coming back!" The team leader suddenly realized and smiled knowingly. "Well, of course, if she keeps spending all day and night in the decryption room, how could she be a proper wife?"

Indeed, Lan Youyin had married a year earlier. Her husband was a lieutenant colonel battalion commander stationed with the Fifth Army in Kunming. Now discharged and reassigned, their long-separated married life was finally coming to an end. Predictable, reasonable.

But where had Lan Youyin’s ambition gone?

Three years later, when Qiao Mingyu was imprisoned for embezzling military funds, her colleagues realized they had underestimated this woman after all—what kind of dutiful wife could carry on as usual after her husband was detained, responding coldly to cautious inquiries: "I don’t know what he did. I have nothing to do with him anymore."

As Lan Youyin left the office, gossip spilled out like beans from a bamboo tube behind her back. Yet the words held nothing new: "I heard she divorced him outright—trying to cut ties in a hurry?"

"Really? Those two days she was absent—was she arranging the divorce?"

"She’s something else. Probably already has someone else lined up."

...

Little did they know, as Lan Youyin walked down the semicircular steps of the Ministry of National Defense, every step landed exactly where she wanted.

The only thing outside her plans was a man named Ren Shaobai.

Ren Shaobai thought Lan Youyin didn’t remember him, because at the defense minister’s inauguration two years earlier, she hadn’t recognized him at all. Years had passed, and he had long grown accustomed to his glasses. From a distance, he spotted the woman in the same military uniform—no, not the girl in the navy-blue dress from seven years ago, but...

"Chief Qiao’s wife from the Third Department. Zhang Pugong introduced them—apparently they had a connection long ago. A beauty, isn’t she? And more than that—she decrypted Japanese codes in Chongqing..." Under Ren Shaobai’s stunned gaze, his colleague gloated as if he were the one who had married the beauty and gained ties to a Nationalist elder. "She’s a section chief now—outranks you."

Ren Shaobai absolutely did not want to examine where that pang of disappointment came from.

"By the way, Shaobai, you’re not getting any younger. Why no prospects? Now that the war’s over, you should think about settling down. Don’t aim too high."Before Ren Shaobai could respond to this, another colleague sitting in the front row turned around and chimed in, "Deputy Section Chief Ren isn't picky. From what I've heard, it's either an old flame he can't let go of or someone he desires but can't have..."

Ren Shaobai promptly kicked him under the seat. "Right in front of me, huh?"

"Is it true, Shaobai? Is there really someone like that?"

"Sure, Shangguan Yunzhu."

...

While Ren Shaobai was busy bantering, he didn’t realize Lan Youyin was also lost in thought, trying to recall where she had seen that familiar-looking man. The inability to find an answer unsettled her, like the conflicting emotions of deciphering a vaguely familiar code—eager yet fearful of stepping into a deliberately laid trap.

In turbulent times, encounters between people were like the numbers in a Sudoku puzzle—no repetition allowed in any row or column.

If there was repetition, something had definitely gone wrong.