Sherlock's hands trembled as he finished reading the letter for the third time. The paper fluttered slightly, the familiar sound breaking the dead silence of 221B Baker Street.

He took a deep, shuddering breath and blinked away the moisture that was causing the precious words to blur. John's words. The last words he would ever communicate to him.

He had no idea how to control the thunderstorm of emotion raging through him. He was drowning in grief, in guilt. These words from his dead best friend were like a lifeline. Something to cling to, to help him keep afloat, help him breathe.

It had been two days since the funeral, five days since Sherlock's world had shattered. He knew he wasn't handling it very well. He hadn't eaten in … a while. He wasn't sure when he'd last slept either. His thoughts were heavy and black; they could easily have bled into uneasy dreams. If they had then sleep was no escape.

Sherlock read the letter again. This time he analyzed every stroke of the standard ballpoint pen John had used. He could tell where John's hand had shaken ever so slightly, adding the slightest wobble to the otherwise straight cross of that 't', the 'i' whose tittle was too carefully stabbed directly above the line. John had taken care in writing this; his usually abysmal handwriting was easily legible, and had Sherlock not known who had written this, he might not have guessed it was a doctor's scrawl. Sherlock imagined John sitting at his kitchen table (or had he written it at the clinic?), hunched over, scrunching up sheet after sheet of ruined paper as he struggled to find the right words.

As his raptor gaze swept once more over the single page, words and phrases seemed to loom out of it, commanding his attention. 'Best man' … 'believe in you' … 'the vow you made at my wedding'.

Sherlock felt the weight of grief crushing him. He screwed his eyes shut and curled in on himself, hoping in vain that it would help. His vow. He had broken it. He had failed. He had let John and Mary die. He couldn't protect them. They were gone.

He shook with silent sobs until the light outside had been replaced by a blanket of darkness, which the streetlamps tried and failed to dispel. He allowed the letter to fall from his grasp and clenched his fists together, despising himself. It should have been him. He should have died instead.

It wasn't your fault, a small but strong voice whispered, and in Sherlock's mind the voice was John's. It was out of your control, a freak accident. Don't blame yourself. I still need you.

Sherlock straightened in his armchair. Yes, he was still needed. He still had work to do, a vow to keep.

Wiping the tears from his cheeks, he took a great breath through his nose and allowed his hands to relax out of the tense fists and lie peacefully on the dark grey arms of the chair. He planted his feet firmly on the ground, and closed his eyes. He had work to do.

His Mind Palace seemed cloaked in darkness as he entered. Grief had manifested itself as black, billowing clouds. Shaking his head and waving an arm imperiously, he banished the dark clouds, paying them no mind as they dissipated into nothing. He would not allow grief free reign through his mind, tainting his thoughts and sapping his strength. It must be controlled.

He strode confidently through the palace of his mind, his footsteps echoing serenely against the bright marble, until he reached a blank stretch of wall. This would do.

Planting his feet firmly on the cool marble floor, shoulder width apart, he thrust his hand forward. The wall before him crumbled and vanished, revealing a void. As Sherlock strode forward, the hole became a door, and the void twisted and swirled until a great room was formed, just in time to support him as he stepped over the newly created threshold.

Now. To work. The most important work.

He stood in the centre of the great room he'd fashioned, and raised his arms, like a conductor. He hesitated a moment, collecting his thoughts. When he was ready, he began.

He started with Mary.

Every detail of every moment he had spent in her company was brought forward into the room. Some memories flew through the open door from other rooms in the Palace, others materialized like smoke before him. He directed each memory into place with slight twitches and jerks of his hands. He did not allow the echoes to touch him; he knew he was not yet strong enough to remember precisely what he had lost.

As all he knew of Mary Watson tumbled into being around him, the grand room began to decorate itself. Normally he would never bother with such things, but he allowed Mary to have her way.

John had begun to form himself in the room too; many of Sherlock's impressions and recollections of Mary were inextricably connected to those of John and, recently, their daughter. He exerted what control he could over the pounding flow of sensation, trying to steer them to their correct place in the room, organize them. Before he came to the last memory, he changed his focus: John.

He had to be methodical; he mustn't forget a single detail. He thought back to their first meeting. The first he had known of Dr. John H. Watson was his footsteps as he and Mike Stamford approached the lab in St Bart's Hospital. His step had been lighter and more uneven than Mike's. Mike had stepped forward to open the door for the limping soldier. Yes, he remembered. He worked from that moment onward, casting connecting webs of thought and impression to other rooms when necessary, connecting John to almost every room in his Mind Palace.

Colour and texture coalesced into John's armchair, which Sherlock set by the newly added fireplace, beside the chair Mary had always favoured in her home. The room was becoming the perfect blend of the flat John had shared with Sherlock, and the home he had with Mary. The two styles fit well together, Mary's brighter choices lightening the tone of the space, making it cozier, warmer.

There was too much - the room was far too small. The flow of memory was slowing; it had nowhere to go. Throwing his arms wide, Sherlock commanded the room to expand. It obeyed. It stretched out into the empty regions of his mind, filling more of the finite space surrounding the Palace. But he mustn't use too much, there were years of memory yet to come. Frowning in concentration, Sherlock cast a shadow of consciousness into some of the least frequented rooms in the Palace, deleting anything that was less important than John - no, that was everything; deleting everything he no longer needed, things that had not proved useful. Everything boring.

As Sherlock catalogued every second spent in the presence of John Watson, meticulously recording every conceivable detail, he felt himself begin to shrink. This was painful. He tried to keep each memory at arm's length, but despite his efforts, many of them still reached him, tore through him, making him feel cold and small and very alone. His shoulders hunched as the thoughts sliced through him, relentless.

He was not strong enough to do this.

He stopped. Sinking to his knees, he stared at the floor with dead eyes. The heart John had thawed had turned to ice once more. It throbbed. It ached. A bullet wound to the chest was nothing compared to this.

A child giggled. Sherlock looked up.

John sat by the fire with Mary, holding the baby up to a ghostly Sherlock. The baby had grabbed his finger and giggled. Apparently it was the first time she had laughed. Her parents beamed at the sound, laughing with her. John's eyebrows rose in surprised delight, casting a wondrous glance up at him. Sherlock had been dumbstruck, not quite understanding that he had made the Little Watson laugh her first laugh.

She giggled again. Sherlock had smiled, his eyes widening in wonder. It was high-pitched and staccato, shrill and unlike any other laugh Sherlock could remember. An odd sound, but surprisingly pleasant. In fact it was the most beautiful laugh he had ever heard.

Sherlock's shoulders slumped. The memory had fractured his broken heart yet again. Surely the pieces would soon be too small to break any further?

Tears tumbled down his cheeks, and he returned his gaze to the floor. There was a carpet there now. Red, trimmed with gold. They had seen it in a suspect's flat and John had commented that, despite being a sadistic murderer, the man had had good taste in rugs. So now it was here.

Two brown leather shoes stepped into Sherlock's field of vision. He looked up, knowing what he would see.

It was John. He was holding his daughter and smiling sadly down at Sherlock. Shifting her tiny weight in his arms, he held a hand out to kneeling detective, the smile widening, warming. He didn't say a word. He simply beamed, his hand outstretched to the broken man before him.

Taking a deep breath, Sherlock grabbed John's hand. The smile grew. With John's help, Sherlock rose to his feet once more. John nodded at him, looking as proud as Sherlock had ever seen him. Sherlock looked down to the Little Watson smiling serenely in her father's arms. She gazed up at him with her wide, bright eyes. He smiled, and closed his eyes, holding the image like a flame to his chest. He would do this. For her.

Back to work.

It was easier now, with his flame protecting him from the sorrow that clung to the memories. He could not allow them to be tainted; he stripped the unnecessary woe from each, leaving them pristine and pure, as they should be.

He conjured an old record player from the aether of his mind and carefully recorded every word he had ever heard John and Mary Watson utter, immortalizing them to record after record. He organised each disc carefully by subject, slotting them into a bookcase that hadn't been there seconds before. Now he would never forget their voices, how they pronounced each word, their laughs, their sighs, all the ways they said 'Sherlock'.

There is no time in the Mind Palace. There is no use for it. He works as quickly as thought will allow for as long as necessary. Sherlock only realised he had been working for a long time when he noticed the slight headache that was forming, which he quickly traced to dehydration. He would drink later - he was almost done.

The flow of memory began to darken. Slipping out from his tight control, the memories he wasn't ready to face erupted into being around him, buffeting him as they passed. He gasped, shocked by their force, and fell to his knee. As he knelt, hunched over and gasping for air that tasted of poison, he looked up. The black memories were tearing through the room, their taint spreading, infecting everything they touched. The flame flickered dangerously as the full force of Sherlock's grief thundered around him, but he would not let it go out. No, no, this could not happen!

Sherlock surged to his feet, roaring his defiance. The black memories stilled, their tendrils retracting slowly, their stains fading from the room around them. Unleashing his mind like so many harpoons he caught each one and dragged them to him.

He stormed over to the most isolated corner, farthest away from the rest of his Palace, and conjured a small room, separate from the grand hall behind him. He commanded the tethered memories inside, and they obeyed, powerless against his resolve. The horrible memories would not taint all the others: they were isolated in this alcove. The call. The denial. Identifying the bodies. The shame. The funeral. He closed his eyes as he left, locking the door securely.

He opened them once back inside the room, only to find that 'room' was no longer the right word. He'd filled an entire wing with memories. He strolled through the halls, looking around at his handiwork, satisfied that he hadn't missed anything, that John and Mary would be content here. He had every word, every scent, every impression and sensation associated with John and Mary Watson firmly remembered now.

When their daughter was old enough to want to know, there was no question he was not prepared to answer fully, and in detail. He would still need to compile physical evidence of course: favourite books, pictures, old clothes that still carried their scent, videos so she would know their voices. The records would only play for Sherlock.

Satisfied with his work, Sherlock strode out of the Watson Wing, closing the double doors carefully behind him. Now, he must wake.

Sherlock Holmes opened his eyes and squinted. Dawn had come and gone and the flat was aglow with sunlight, floating through the empty space, streaming through the tall windows behind him. He must have worked all night and well into the morning.

His gaze swept through the flat, taking in every detail. He would have to make some changes. His equipment had to go - he'd keep it in his room, or at Bart's. He'd have to find somewhere else to keep his knives too; many of them were within reach of small hands. Hm. The entire flat should be baby-proofed, and he'd have to make room for everything Little Watson would need.

John's chair would stay of course. It would be her chair now.

He must learn to cook. A child could not be raised on take-out and toast. Mrs. Hudson could teach him. There was much more he would have to learn, and quickly.

His head throbbed dully. He needed water. And food, probably, though he didn't feel hungry.

He rose fluidly from his armchair, ignoring the stiffness of his limbs. He picked up the precious letter and set it carefully on the table by his chair. Striding into the kitchen, he put on the kettle, and then checked the fridge for food. Mrs. Hudson had been to the supermarket - there was enough for a veritable feast crammed onto the shelves. She must be very worried indeed to have bought this much food, knowing how little he usually ate. Sherlock smiled. He would go down to her once he'd eaten. He hadn't spoken since the funeral. He knew she was grieving too; he wasn't the only one who had loved John and Mary. Not the only one with a hole blasted through their heart.

He would fight the heavy blackness that had descended upon him. And he would beat it. He would not raise John's child in misery. He must make her laugh, and so he must be capable of laughing. Hope was not lost. There was one Watson left, one last chance to keep his vow. He would do as John had asked.

The kettle had boiled. Sherlock dropped a teabag into the teapot and fetched the milk and a tin of beans, which he poured into a pot on the hob.

He could not refuse John Watson anything. He would never forgive himself for breaking his vow, but he would not let his regret and shame rule him, and he would not let it show. He would be the godfather John wanted him to be. He would do anything for John, anything and everything. Even eat, though he wasn't hungry.

AN: This story continues inLittle Watson as Sherlock adapts to life as a godfather. Click on my profile to see it!

Huge thank you to all you lovely reviewers, I wouldn't have written this if you weren't so supportive!