The moment the words left the mouths of the renowned detective and the professor of criminology at the same time, the stagnant air of the study felt as though it had been sliced open by a sharp blade.
In that instant the two girls transcended opposing camps and differing personalities, displaying a remarkable tacit understanding.
"A public, rational, and wide-area broadcasting system that can cover the entire United Kingdom simultaneously."
Charlotte's eyes suddenly lit up and her speech quickened.
"He owns three influential print-media companies with very high sales in Birmingham, and he also has extensive connections on Fleet Street. If he needs to send security codes to the various keepers scattered across Britain, the safest and least conspicuous method would be to hide them in the daily newspapers."
"The truly clever live quietly in the middle of a bustling street."
Mary interrupted Charlotte.
"Just like when we once hid a murderer's corpse in the Whitechapel district."
The girl's white fingers lightly tapped the table, producing a rhythmic sound.
"The keepers don't even need to know what the security code means. Every morning they only have to spend one cent on a newspaper and open a specific page. It might be a missing-persons notice, a string of meaningless letters in the corner of a crossword puzzle, or an unfamiliar word in the weather forecast. As long as that mark remains, they will continue to lie in wait. If the mark fails to appear for several consecutive days—"
"Then the Pandora's box sealed by Appled will be completely opened."
Russell sat deeply in his chair, watching the two of them take turns performing.
"Because this system requires him to transmit the security code regularly, he must contact the newspaper companies. And as long as we know that security code and how he delivers it to the newspapers, we can replace him and become the new Milverton. As long as the broadcast continues, the Sword of Damocles hanging over the whole of Britain will remain hanging there forever."
"Easier said than done."
Charlotte shifted in her chair. Her wording remained sharp, yet the admiration in her eyes was unmistakable.
"But the problem is where in the newspaper the security code can be hidden."
"Let's narrow it down by conditions first."
Mary said, "The newspaper must have a sufficient readership, and there must be a column where the security code can be placed clearly without looking unnatural."
"There can't possibly be only one such newspaper covering the whole of Britain."
Charlotte said.
"One serving isn't enough—we need more."
Mary continued.
"The Daily Telegraph, The Daily Mail, The Daily Express, The Times, The Guardian… One plan targets London, another targets Birmingham, yet another targets Sheffield… But looking at the results, it doesn't seem like pure fantasy."
Charlotte was slightly surprised, yet immediately understood what she meant.
"But that would mean a large-scale search comparable in scale to the British Library."
Russell poured cold water on the idea.
"Every day an uncountable number of newspaper pages are published. If he really hid the security code in trivial text—even something as short as a few characters or a weather forecast of fixed length—without the key it would be no different from trying to haul up a murderer's body sunk somewhere in the Thames."
"It's impossible for him to hide it in a place like that."
Charlotte said.
"If he intended to take into account every person who subscribes to a newspaper, he could never hide the password in such a place. Articles and reports are dense; not everyone has the patience to read them sentence by sentence. From this we can almost rule out combinations of letters. I think it is more reasonable to assume he used numbers as the security code. Looking through an entire newspaper, there are almost no places where numbers can be published without any restriction and without attracting attention."
Mary picked up a newspaper, spread it on the table, and lightly tapped it with her finger.
"Job advertisements…"
Charlotte immediately found the dense black lettering in the centre of the paper.
"Or Sudoku."
…
Four o'clock in the afternoon.
Winter London grew dark very early; brass gas lamps were already lit along the streets.
The reception room that had once been decorated with expensive paintings and velvet sofas was now completely buried under thousands of old newspapers.
Mary and Charlotte each sat at a large, long table at opposite ends of the reception room. Two young women beautiful enough to draw countless admiring sighs in London high society were now buried under mountains of newspapers, staring with sharp eyes at those dry letters and numbers.
"Found it."
Mary suddenly flung away the paper knife in her hand and spoke in an excited tone. The girl stretched out her hand, gathered the newspaper clippings of the past seven days, and pushed them in front of Charlotte and Russell.
"This sixteen-cell grid shows four predicted values for each day. From the cells that contain these four-digit numbers, extract the digits from left to right and top to bottom to form a four-digit number. Then subtract the date and the year from that four-digit number."
Charlotte's ash-blue eyes suddenly shone; she finished the calculation in her head in an instant.
"A constant combination of numbers is obtained: 1895."
She suddenly looked up at Mary.
"The year Milverton and his mother were expelled from London by Arthur Morstan, and the year his mother died of hunger and cold, was 1895."
Mary understood the meaning of that number almost immediately.
"What a detestable classical villain."
Charlotte threw the pencil in her hand onto the table with a contemptuous sound. Yet the frown that had been carved between her brows all day finally disappeared completely in this moment.
The mystery was solved.
The Appled Dead Hand system, which had seemed perfect, untraceable and untouchable, had exposed its most critical lifeline in this reception room that still carried the smell of ink.
"Now only one question remains."
Russell said.
"How do we take control of this system? We know the cipher of Pandora's box, but the problem is how we can control it."
"That's not something I need to think about."
Charlotte collapsed into her chair and pinched the bridge of her nose.
"My brain cells are already exhausted enough. I need rest."
"These Sudoku puzzles are usually created by a single person. Generally speaking, it is rare for a newspaper company to specially commission its own reporters to invent such puzzles. Therefore they usually outsource them."
Mary said.
"So we only need to find that outsourcing company?"
Russell raised one eyebrow.
"It sounds as though the difficulty has dropped considerably."
"Then I'll leave this matter to you."
Charlotte waved her hand.
"As if I ever had a choice."
Russell shrugged, took his coat from the back of the chair and casually draped it over his arm.
"But now that the cipher pattern has been deciphered, all that remains is physical labour. You two brilliant detectives who have overworked your brains should rest for a while."
"That sounds more like human speech."
Charlotte accepted the offer without hesitation. She stood up from the chair, rubbed her slightly aching neck, and casually wiped her pencil-dust-covered hands with a handkerchief.
"There's nothing more for me to do here, so I'm returning to Baker Street."
She walked to the door, picked up her coat, then glanced back at the two of them.
"Don't blame me for not warning you. The fact that that fox Milverton sent a letter means he is definitely prepared for every contingency. When you go to the outsourcing company, act carefully so they don't notice you."
"Don't worry—I'm a professional thief."
Russell waved to her.
Mary walked to the washbasin in the study, turned the brass tap, and carefully washed the cheap ink stains from her fingertips. Amid the sound of running water she looked at the man standing behind her adjusting his collar through the decorative mercury mirror in front of her.
"Fleet Street is at its busiest right now. All the major newspaper companies are preparing tomorrow's morning editions."
The girl took a pure-white dry towel, wiped her hands, then turned and leaned against the edge of the washbasin.
"Which newspaper does the phantom thief intend to start investigating from?"
"Since the password is published simultaneously in multiple newspapers, let's choose the largest one."
Russell casually wrapped a scarf around his neck.
"I still have some connection with The Times. Even in the worst case I can simply say Moriarty told me to do it."
"If we can trace the signature on the payment settlement documents and locate the address of the outsourcing company that supplies the Sudoku puzzles, we should be able to find Appled's lifeline."
"That sounds like a good plan."
Mary stepped closer to him and naturally reached out to straighten his dark-grey cashmere scarf.
"Be careful."
The girl did not try to persuade him to stay any longer; she spoke quietly.
…
Eleven o'clock at night.
While the gentlemen of London's West End were sleeping soundly in warm feather quilts and the workers of the East End were shivering in the cold wind, Fleet Street entered the liveliest hours of the day and overflowed with energy. This was the core of London public opinion.
Russell pulled down the brim of his hat, turned up the collar of his coat, and, like a drop of ink, naturally melted into the crowd of people hurrying through the night streets. He pushed open the door of The Times and walked straight in.
The receptionist recognised Russell and greeted him warmly.
"Good evening, Mr Russell."
"Good evening."
Russell nodded. "Is Mr Henry in?"
"Yes. Are you looking for him?"
"Yes, I have a few questions for him."
"Please wait a moment."
The receptionist said this, then turned and left for a short while. Before long Russell saw a familiar figure coming down the stairs.
"It's been a long time, Mr Russell."
Henry waved to him.
"So you've finally decided to give me a headline today?"
"He didn't mention anything about headline, but he asked me to ask you something."
Russell shrugged.
Hearing this, Henry's smile froze and gradually turned serious.
"Please come up and have some tea."
He stopped and gestured for Russell to follow.
Second floor, reception room.
Russell sat on the sofa, accepted the black tea Henry offered, and took a sip. Still not as good as William's.
"So, Mr Moriarty, what would you like to ask?"
Henry asked in a low voice.
"Was the Sudoku section of The Times created independently by your own reporters?"
Russell asked.
"Sudoku?"
Henry raised one eyebrow. "No, our reporters aren't that free." He seemed not to understand why the question had been asked.
"Actually this section started simply because we didn't know what to write, so we just put something in. Before we knew it, it had become a habit."
"Where do you obtain them?"
Russell asked.
"Outsourcing is usually done by small individual studios; it's just one of the ways they earn side income."
Henry said.
"Why is Mr Moriarty interested in this?"
"The boss's mind always works faster than ordinary people's."
Russell sat deeply in the velvet sofa and spoke in a rather casual, teasing tone.
"He probably tried a few number games out of boredom and then became curious about the person who set the problems."
Henry's hand holding the teacup trembled almost imperceptibly; one or two drops of hot tea spilled. As an editor who had spent most of his life on Fleet Street, he knew all too well what it meant when a monster like the Moriarty of urban legend took an interest in something. It was by no means an honour to be celebrated.
"Ahem… so that's it."
Henry gave a light cough to cover his misunderstanding and wisely chose not to dig deeper into the conspiracy behind it. He stood up, walked to the heavy oak filing cabinets lined against the wall, skilfully pulled out one of the drawers, and rummaged inside for a while.
"Found it. This is it."
Henry took out a yellowed accounting slip and handed it to Russell.
"Because of staff shortages we outsourced this section three months ago. Since then this studio has been supplying Sudoku games to The Times and several other major newspapers. The fee is extremely low, almost as if they're paying out of their own pockets, and they have never once missed a deadline. As far as the editorial department is concerned, as long as the blank page can be filled, we don't care who creates the problems."
Russell accepted the signed document and immediately scanned it. The form contained only basic payment information; the recipient column was written in an illegible italic script, and the address was rather distant.
[Iliad Finch, back alley of Charing Cross, second-hand bookstore and stationery shop.]
Russell frowned, instinctively sensing that something was off.
"Is there a problem?"
Henry noticed the furrow between Russell's brows and asked.
"Is this everything?"
Russell asked.
"Yes, that's all."
Henry nodded honestly. "It's a daily-rate system; that's all there is."
Hearing this, Russell asked nothing further.
"Thank you, Mr Henry."
He set down the teacup, stood up, and said, "I have to go back and report."
"Ah, I understand. Take care, Mr Russell. Next time something newsworthy happens, please do contact me!"
Russell waved and prepared to leave the building.