A/N: Up until this chapter, I had a vague notion of the cipher. So as I set upon trying to make it as real as possible, I realized I knew diddly squat about music or playing the violin, though I could fake my way through relatively simple 19th century cryptography. However, since my idea hinged on finger positions on the violin, I had to do (too much) research again :) I'm sure if anyone actually plays violin, they may be able to tell me I've screwed something up, and those that don't might find those paragraphs gibberish. I tried to make it simple for myself and others. I tried. :) Enjoy :)

Anderson had, as Sherlock supposed, left the majority of the bodies alone. Several had been identified and released to the families for burial, but the rest had been moved to the far end of the morgue so Anderson could continue on with his day-to-day corpses, the ones which came down from the hospital above and would not exhibit the same strange lack of decay. Sherlock pulled back a few of the sheets, choosing the body he would examine first with care. He was briefly distracted by wondering how long the bodies would remain in their current state, exposed to room temperature (even given that the morgue was much cooler than an average sitting room with a fireplace). He pushed away the thought for later and selected the body of a barrel-chested man.

The body had not been autopsied yet, the better to not have contaminated the pattern by snipping the black threads. This corpse had received an amputation of all limbs and a complete removal of the chest plate before being pieced back together. Sherlock considered a moment and decided the chest wound was the most likely area for the message to have been spelled out – certainly 'raphe' had been written on Lazarus' chest, and that ought to be a clue. He leaned close and examined the stitching that marched from shoulder to shoulder, shoulder to waist, across the belly and back up again.

And there it was: repetition of spacing, here, there. He placed a fingertip gently between the marks in several places, estimating measurements. A substitution cipher would be the most obvious of choices, something simple and solvable without a key. If one assigned the most repeated variable with the most common letter "E," for instance, the message often began to reveal itself. However, no particular spacing was definitively frequent enough. Perhaps if the measurements related to the positional numbers of the alphabet, A=1, B=2… no, that was gibberish. It wasn't so simple, then. Not surprising.

"Is there anything I can help you with, Sherlock? What are we looking for?" John arrived at Sherlock's back. Sherlock shook his head. Focus. But it was no use. All he was aware of was John moving to stand by his side.

"There's a pattern." Sherlock experienced an all-too-familiar moment of self-loathing. "I can't believe I didn't recognize it. I was too overwhelmed, too distracted." Much like I'm distracted now. "I had to be told. It was a simply unforgivable mistake."

"What sort of pattern?" John stepped forward and leaned over the body to peer at the black threads. His eyes were wide and there was a hint of a smile on his face. Of course there was. John was interested in his work, in the excitement of a case. That was what made him so…

"Here, and here, see?" Sherlock answered, pointing out the repetition of the widest spacing, precise and occupying three positions down the length of the torso. They were followed by several more narrow stitches in each case. "You said there was something odd about the spacing between the sutures, though they themselves were executed with finesse. The spacing is a code, a cipher."

"Can you decipher it?"

"Of course. I simply have to note the measurements and see what I have to work with." That was a lie. If the cipher is what I think, I shall simply have to read the message so patronizingly spelled out for me.

"And you got all this from raphe? That's positively brilliant, Sherlock." John beamed. I don't deserve that smile.

"It's not, John!" Sherlock shouted. He flung his hands in the air and stomped his feet in frustration. "I had to be told. That is why the markings on the man at Bow Street were so fresh. I wasn't seeing it. I wasn't understanding! Whoever this is had to tell me where to look. I've been so blind, so distracted!" I've let this all happen, blind as any other imbecile on the street.

Don't look at me that way, John. Sherlock could avert his eyes, but he couldn't close his ears.

"Just tell me what I can do to help, Sherlock."

"You can leave me alone to take the measurements so I don't make another stupid mistake, or miss something right in front of my eyes!"

Sherlock's face and eyes were hot and his ears thrummed with his agitated heartbeat. He barely heard John mutter something about Stamford and make his exit.

Sherlock took a deep, shaky breath. He imagined an impenetrable tower encapsulating him and the body in front of him. Nothing else existed. Gradually, his heart slowed and his mind narrowed to his task. There was no room to worry about consequences, no thought beyond the code in front of him.

And suddenly, the spaces between the black lines of thread looked very familiar indeed.

It had been several years since Sherlock had thought about coding messages. It was a familiar pastime while he attended university. He'd once written an entire thesis entirely in code, a book cipher. When he'd turned in pages upon pages of number pairs, he had expected to be disciplined at the very least, sent down at the worst. His professor, however, had been entertained and intrigued, and suddenly Sherlock found university much less dull indeed.

Cryptography was useful knowledge, so he'd never deleted the skill even if he ceased his dabbling. Mycroft, with his advisory position to the Regent, was especially expert at it, reading certain forms as fluently as English or French. However, he had not spent the time mastering a musical instrument, as Sherlock had. Thus, while the Viscount could appreciate fine music and converse about the biographies of centuries of composers, he had no real practical knowledge of making music.

And that's where this cipher spoke.

The code wasn't exactly a substitution cipher, but closer to a musical cryptogram, with similarities to the BACH motif. Notes corresponded to certain letters; flats, sharps and naturals helped to expand the limited musical alphabet. Johann Sebastian Bach, for example, would use a recurring succession of the notes B flat, A, C, and B natural, (written as H in German musical nomenclature), in his works, thus the name.

This particular cipher, developed to aid in deceiving Mycroft when the need arose, would use the finger placement of either the violin or piano to lead to such notes. The lines on the bodies, the placement of the stiff black thread, felt like violin strings beneath Sherlock's fingertips. Or perhaps if he placed his fingers within the spaces, he would feel piano chords in the stretch of his phalanges. He could read this – he'd helped develop it.

The revelation should have gladdened Sherlock – he had his fingers on the solution – but instead he felt ill. This development infinitely narrowed down the field of suspects. Sherlock had only shared this cipher with two others.

An "Oof," pushed a brick out of the wall Sherlock had built around himself; the brick hit the ground with a similar sound in Sherlock's mind. Anderson was the source of the noise; John had roughly shouldered him aside upon reentry to the room. When had Anderson been in here? And John had not been gone nearly long enough. Sherlock had hoped to decipher this body and… and figure out whatever brilliant plan he must come up with to end this.

Sherlock's mind rattled too quickly down this route to process John's brusque statement immediately. "Sherlock, I need you to listen to me for a minute."

By the time Sherlock had processed the words, John had already reached out and grabbed Sherlock's wrist.

"Is this interruption necessary, John?" he said to give himself another moment to catch up.

"I shall make this short. You were right about the explosion on the London Docks. I'm headed there now with Stamford and some of his medical students to offer my help with the wounded. I'm not certain how late I will be, but I will see you at home when the situation is under control."

"Is that all?" John would be very busy until late tonight, most likely, perhaps longer. Would that be enough time to finish this? To keep John out of this mess? It would have to be.

"Yes, I suppose it is."

John left the room, buttoning his coat, his back stiff and straight.

No more time to think about John. Sherlock pushed the one fallen brick back into the wall around his brain and studied the lines in front of him. Eight lines preceded the first gap in stitches. Sherlock placed his fingers on the longest of the stitches. If the shorter spaces between the lines indicated half-steps, then the line of stitches could represent the first position fingering for the D or A strings on a violin. The second string from the right was the longest, the only long string. Sherlock closed his eyes to imagine a violin under his fingertips; the position of having his fingers facing forward instead of uplifted and twisted towards him was awkward. If only his forefinger was pressed to a string, in that position… Hmm, E natural or F flat on a D string or a B natural on the A string. On the chart long since developed and memorized, Sherlock looked for the corresponding letter. E or M, or possibly B. He used a stub of pencil to scrawl these letters on the nearest piece of paper.

Sherlock moved to the next set of lines. Definitely the G string this time, from the lines representing the steps and half-steps. The longest line was at low 2, representing A sharp or B flat. B flat would be the letter I, with A sharp representing O. Sherlock moved to the next quickly this time, certain he'd found the right key to solving this.

The rest of the letters quickly dropped into place. After the pattern had repeated wholly, Sherlock stopped and examined the letters for the first eight letters of the cipher, some positions having more options than others. It wasn't long before he comprehended the word which repeated in the stitching before him.