The early morning sunlight filtered through the foggy London air, casting a soft glow over 221B Baker Street. Inside the cozy apartment, Mrs. Hudson hummed to herself as she set the kettle on the stove. Today was no ordinary day, though it would take a man of Sherlock Holmes' peculiar genius to uncover that. Mrs. Hudson was not in her usual quiet mood-no, today she was brimming with the kind of secret anticipation reserved for grand schemes.

Watson descended the stairs, a small grin tugging at his lips. He entered the kitchen and nodded to Mrs. Hudson, whose conspiratorial smile grew wide as she handed him a cup of tea.

"All set, Mrs. Hudson?" Watson whispered, his eyes twinkling.

She gave an enthusiastic nod. "Everything is prepared. Oh, Dr. Watson, do you think he'll notice right away?"

Watson chuckled softly. "Sherlock? He'll suspect something in ten minutes, no doubt. But if we play it right, we might still catch him by surprise."

"Goodness me, I do hope so," Mrs. Hudson said, her voice a tad breathless. "He's never celebrated a birthday before, has he?"

"Not that I know of," Watson replied, sipping his tea. "And believe me, I've tried. He insists it's frivolous, but I have a feeling this might finally break his icy demeanor."

They both shared a knowing glance. The plan had been laid out over the past week with meticulous care, worthy of Holmes' own standards of precision and planning. Small puzzles scattered about the apartment would lead him to his inevitable fate: a birthday celebration, whether he liked it or not. Each clue would seem disconnected, but they would all converge in one unexpected conclusion.

Watson placed his cup down and stood straight. "It's time."

As if on cue, Sherlock Holmes emerged from his room upstairs, his dressing gown flaring like a cape behind him. His sharp eyes darted from Watson to Mrs. Hudson, instantly detecting the shift in atmosphere. He narrowed his gaze suspiciously, but said nothing as he walked past them, heading for the sitting room.

"Morning, Sherlock!" Watson said, trying to sound as casual as possible. "I trust you slept well?"

Sherlock paused mid-step, tilting his head slightly. "A strange question, Watson. What are you up to?"

"Me? Up to something? I'm insulted," Watson replied with feigned indignation. He busied himself by picking up a medical journal from the armchair and flipping it open, though he could feel Sherlock's piercing gaze upon him.

Mrs. Hudson, clearly struggling to maintain her composure, excused herself in a flurry. "Oh, I must fetch something from the kitchen!" she called over her shoulder as she practically bolted from the room.

Sherlock arched an eyebrow. "Suspicious," he muttered, folding his arms. "Very suspicious indeed."

Before Sherlock could probe further, a knock came at the door.

"Ah, that must be the post!" Watson said, leaping up a little too eagerly. Sherlock's eyes narrowed again. Watson's behavior was off-unnaturally chipper and too quick to act. Sherlock moved to the window, peering through the curtains as Watson retrieved the letter.

"How curious," Watson said, holding up the envelope. "It's addressed to you, Sherlock."

Holmes strode over, snatched the letter from Watson's hand, and examined it with keen interest. The envelope was plain, save for a rather smudged postmark, and the handwriting was unfamiliar. Sherlock opened it swiftly, eyes darting over the note inside. His brow furrowed.

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"Interesting," he muttered. "A riddle."

Watson leaned in. "What does it say?"

Sherlock read aloud: "'What is seen once in a lifetime, twice in a moment, but never in a hundred years?'"

Watson feigned a thoughtful expression. "A curious puzzle, Sherlock."

"It's an elementary riddle," Sherlock replied, his tone clipped. "The answer is the letter 'M.' But why would someone bother sending me such a trivial thing?" He tapped the note against his palm, looking perplexed. "I despise this kind of petty amusement."

Watson suppressed a grin. The game was already afoot.

Holmes, never one to leave any mystery unsolved, was already turning the letter over, searching for more clues. A small slip of paper fell from the envelope, and Sherlock caught it with practiced ease.

"There's more," he murmured, unfolding the scrap of paper. "An address."

It led to a small shop not far from Baker Street. Sherlock's eyes gleamed with curiosity, though he would never admit it outright. Before Watson could utter another word, Sherlock was already reaching for his coat.

"Are you coming, Watson, or are you going to sit there all day with that insufferable smirk on your face?"

Watson hurried to his feet, grabbing his own coat. "Of course, Sherlock. Wouldn't miss it."

***

The small shop turned out to be an antiquarian's curiosity, filled with trinkets and oddities, the sort of place where one might stumble upon a forgotten treasure-or an elaborate prank. The bell above the door jingled as they entered, and a wizened old man looked up from behind the counter.

"Ah, Mr. Holmes," the shopkeeper said with a crooked smile. "I've been expecting you."

"Have you now?" Sherlock asked, his tone icy. "And why might that be?"

The old man chuckled and reached under the counter, producing a small box wrapped in brown paper. "This arrived for you early this morning. Special delivery."

Holmes took the package without hesitation and tore away the paper. Inside was another note, this one much more cryptic than the last: "From the place where the hands of time do not move, look beneath what has long since passed."

Sherlock's eyes flickered with intrigue, though he kept his face impassive. Watson could see the gears turning in his friend's mind.

"Watson, we're going back to Baker Street," Sherlock declared, his voice sharp. "I know where this leads."

***

Back at 221B Baker Street, Sherlock wasted no time. He moved with precision, scanning the room until his eyes settled on the old grandfather clock by the window. With swift movements, he pulled it away from the wall, revealing a dusty ledger hidden beneath. Inside the ledger was a third note: "The key is hidden where stories are spun, and the game is won."

"Stories are spun?" Sherlock muttered, his brow furrowing. "The answer must be the bookshelf." He crossed the room in quick strides, running his fingers along the spines of the volumes. His hand paused over one particular book-an anthology of old folktales. He tugged it free, and from the pages, a small brass key dropped into his hand.

"Another key," he said, holding it up to the light. "But to what?"

Watson, leaning against the mantel, did his best to suppress his amusement. "What do you think, Sherlock? Where could it possibly lead?"

Sherlock shot him a sharp glance, then pocketed the key. "It's time to solve this. There's only one place left to check."

Without further explanation, he strode upstairs to his own room. Watson followed, heart racing in anticipation.

Inside Sherlock's bedroom, the detective immediately approached his locked trunk, where he kept various personal effects and important case documents. The brass key fit perfectly in the lock, and with a twist, the trunk popped open.

Inside, to Sherlock's visible confusion, was a cake. A cake adorned with candles and a small note tucked into the icing that read: "Happy Birthday, Sherlock!"

Watson, unable to hold back his laughter any longer, clapped Sherlock on the shoulder. "Surprise!"

Sherlock blinked, staring at the cake as if it were a bomb waiting to explode. "A... cake?"

Mrs. Hudson appeared in the doorway, beaming. "Oh, Mr. Holmes, I do hope you're not too cross. It's just that we thought-"

Sherlock held up a hand, silencing her mid-sentence. He looked from the cake to Watson, then back to Mrs. Hudson. "You planned all of this?"

Watson nodded. "It was Mrs. Hudson's idea, really. I merely assisted. A little birthday surprise, Sherlock."

For a moment, Sherlock stood in stunned silence, as if his mind were processing the concept of a birthday celebration. Then, to Watson's great astonishment, Sherlock let out a small, reluctant chuckle.

"I see," he said, though his voice still held a trace of bemusement. "So this entire day-the riddles, the clues-they were all leading to this?"

"Precisely," Watson said, smiling. "Happy Birthday, Sherlock."

Sherlock sighed, but there was a softness in his expression, a faint gleam in his eyes. "You know, Watson," he said, picking up a fork and examining the cake with the same scrutiny he would reserve for a crime scene, "I think I despise birthdays a little less now."

And with that, Sherlock Holmes, the greatest detective in London, took a bite of cake, much to Mrs. Hudson's and Watson's delight.