John entered the flat to see Mycroft standing beside his brother, who was sulking on the couch.
"Ah, John Watson. I'll leave him in your capable hands," he said, referring to Sherlock.
"Well then. Any news?" John asked after Mycroft had gone.
Sherlock sneered. "I'm under house arrest."
John noticed the ankle bracelet poking out from under his trousers. "You're under house arrest?" he asked.
"How do they expect me to get anywhere with this case if I can't leave the flat?" Sherlock complained.
"Well you have just killed a man," John pointed out. "Most people wouldn't like the idea of you wandering the streets scot-free."
"I'll have to rely entirely on my homeless network," Sherlock muttered.
"Need me to do anything for you?" John asked.
"Nope."
"Your homeless network already on it then?"
"No idea."
"Then what are we doing to stop Moriarty?" John wondered.
"Nothing at the moment," Sherlock replied.
"Nothing? Moriarty is back and we're doing nothing?"
"We need to wait for him to make the first move."
John was flabbergasted.
"I've got some new board games if you're interested." Sherlock told him as he stood.
"No, Sherlock, we're not playing games while Moriarty is at large."
"Why not?" Sherlock asked, confused.
"My God," John laughed in disgust, "I can't believe you're not taking this seriously!"
"Of course I'm taking this seriously, John!" Sherlock shouted. "But there's nothing I can do! I've got nothing to go on, I've 'just killed a man', and I can't even leave the flat!"
John nodded as he pursed his lips. "Alright, Sherlock. I'm going home. Let me know if anything comes up."
Sherlock sighed. "John-"
The door slammed as John left, his footsteps growing softer as he descended the stairs.
Sherlock's phone buzzed.
Got something you might be interested in
W
Sherlock smiled.
Half an hour later, Mrs. Hudson's shrieks were heard from below as three disheveled-looking boys entered the flat.
"Where's Wiggins?" Sherlock sighed.
"'e told us to deliver this to you, Mister 'olmes." One of the boys explained as he held out an envelope.
Sherlock paid him a few pounds in exchange. "Next time tell him to bring it himself. I can't have all of you running about and scaring the landlady."
"Yes sir, Mister 'olmes," the boys promised as they left.
Sherlock opened the envelope and unfolded the note inside. It was from Fred Porlock, he recognized the writing. The flourish over the Greek 'e' was distinctive. Porlock was one of his insiders he had employed to get information on Moriarty. Sherlock stared at the slip of paper, absorbed in his thoughts.
John had been home for about forty-five minutes before he received a text from Sherlock.
BAKER STREET AT ONCE
IT'S OUR MOVE
SH
John got up and grabbed his coat. "Mary I've got to go, Sherlock says he's found something. I won't be too long."
Mary looked up from her book and watched her husband leave. The door slammed to a close and she stared ahead, thinking.
John rushed up to the flat. Sherlock was at his desk, focused on a scrap of paper. John walked over to him. "What's that?"
"A message. From one of my informers on Moriarty."
John looked over Sherlock's shoulder at the note upon which was scrawled:
534 C2 13 127 36 4 21
13 37 BIRLSTONE
"Is it some sort of code?" he asked.
"Clearly," Sherlock replied. "It's some sort of cypher. We just need to find out what book is being used."
"Book?" John questioned.
"Yes, it's obviously referring to words on the page of some book."
"Why didn't they encode 'Birlstone'?"
"Well presumably because it's not found on the page in question"
"Why didn't he leave a note telling you what book the code's referring to?"
Sherlock sighed. "It would be a critical error to conceal both the cypher and message in the same envelope, should it be miscarried. A second letter shall be here any moment revealing the exact book we need."
A few moments later, Billy arrived with the second envelope just as Sherlock had expected.
"Ah, now we're getting somewhere." Sherlock claimed, excitedly. But his brow clouded as he scanned the note.
"What is it?" John asked. "What does it say?"
"Dear Mister Holmes," Sherlock read. "I can't go on with this matter any further. He suspects me. I can feel that he suspects me. Burn the cipher I previously sent, it can be of no use to you. Fred Porlock."
"Well there goes that lead." John said futilely.
Sherlock sat holding the note, lost in thought. Suddenly he exclaimed, "Unless there are some points which have escaped your Machiavellian intellect." He stood and began pacing back and forth anxiously. "Let's consider the facts, what we have to go off of. This particular cipher is based on a book."
"Yes, narrowed it down quite a bit there."
"What clues do we have as to which book it is referring to?" Sherlock asked, ignoring John's comment.
"None," John replied.
"Ah, that's where you're wrong," Sherlock smiled. "Look here," he said, pointing to the code. "The first number is 543, if that is referring to page number we can infer that it is a very large book, which narrows our field a bit. What next? We see C2, what do you think that could mean?"
"Chapter two?" John guessed.
Sherlock scoffed. "Really, John? Chapter two starting after page five hundred forty-three? It's clearly indicating column two."
"Well that's it then?" John asked. "A big book with columns?"
"I don't think we've quite exhausted our knowledge of this book," Sherlock hinted. "Had the book been esoteric in nature, it would have been sent to us."
"Which means it must be common," John gathered.
"Precisely," Sherlock said as he made his way to the book shelves. "This was a book Porlock had and assumed I would have as well."
"The Bible?" John tried.
"No, too many versions, it'd be far too unreliable," Sherlock disparaged. "No, this book had to be something standardized something that would be easy to correspond."
"So a large, standardized book with columns that most people own," John summarized. "A dictionary or some sort of almanac?"
"A dictionary's vocabulary would be difficult to make into general messages; let's go with the latter."
Sherlock rummaged through the rows of books until he found the almanac. He quickly decoded the message aloud, as John recorded it.
"There… Is… Danger… Coming… Soon… Target… At… Birlstone."
"What's that supposed to mean?" John wondered.
"Someone presumably at Birlstone is in danger."