John wasn't quite sure why he had decided to go walking in the park. All he knew was that if he stayed for one more moment in that claustrophobic room he'd start throwing chairs.

The soreness in his leg was akin to an itch that couldn't be scratched. It throbbed in a different way to his shoulder and every step he took sent a small flare of pain up his body. It's not that John was in his own world so much as he paid no attention the present one surrounding him. Plus, it had been so long since he'd talked to anyone except his therapist that he could be forgiven in not hearing his name being called twice from behind him.

"John! John Watson!" He turned to face a man whose shirt strained at the waist, hastily tucked into cheap, high-street work trousers. Despite the unthreatening air John was unable to prevent the initial shot of wariness he knew now was a leftover reaction.

"Stamford. Mike Stamford, we were at Barts together?"

"Yes sorry. Yes, Mike." Recognition faltered through and John shook his old school friends hand, careful to ensure it was his right so Mike wouldn't feel the tell-tale tremor.

"Yeah I know, I got fat" Stamford chuckled.

"No, no" John remembered how Mikes eyes used to look. They had always been friendly, mottled with what scientists commonly called the 'warmer' colours. The silver and gold of love and companionship had complimented the softer green and blue hues of intelligence and geniality.

"I heard you were abroad somewhere, getting shot at. What happened?"

"I got shot." His look was uncomfortable, when he finally risked a glance at Mike's eyes he was unsurprised to find the colours had merely deepened with time. His old school friend guarded his expression carefully but John saw the look of surprise and pity that quickly flashed across Mike's expression. It was a look John was growing accustomed to, he knew how much his eye colour had changed. With nothing to keep them there the purple and gray had faded leaving behind clashing midnight blue with streaks of orange and the painful brown of loneliness.

"Coffee?" asked Mike.

It was ironic, John mused, that the colour denoting happiness was also a signifier of unhappiness. Yin and yang. The darker the blue the deeper the sadness ran. John was one of the humans that didn't enjoy his emotions on display as was the case in their species. It was a blessing, and a curse, he supposed, that an emotion had to be felt deeply for the colours to resonate rather than flicker. He was infinitely grateful that human irises were usually about the size of a penny, only to the extremely observant were more than three or four colours obvious.

Mike had been speaking, John realised, something about London. He couldn't quite stem the bitterness that welled up and his reply came out more snappily than he intended.

"Can't afford London on an army pension."

"Ah, and you couldn't bear to be anywhere else," said Mike jovially "that's not the John Watson I know."

"I'm not the John Watson you-" John bit off suddenly but it was too late and now a heavy uncomfortable atmosphere hung in the air.

"Harry couldn't help?" Mike ventured. "Or a flatshare?"

At Mike's first suggestion John had sniffed, at his second he couldn't help the snort of derision and disbelief that escaped.

"C'mon. Who'd want me as a flatmate?"

Mike said nothing but his smile was enigmatic.

"What?"

"You're the second person to say that to me today."

John both hated and chased the feeling of interested that ran through him.

"Who was the first?"

John had been surprised to find himself at St. Barts - his old medical school, and even more surprised when Mike had led him down to a quieter part of the hospital not too far from the morgue.

"Listen," Mike stopped a few feet from a pair of double doors. "I should warn you about something before you go in."

"What?" John felt the trepidation and quelled it before the emotion could reflect.

"He's got a bit of...well, a condition." Mike explained reluctantly.

"A condition?"

"Just, don't mention his eyes." With that bizarre warning Mike walked through the door, holding it open for John to limp in after him, his leg still protesting from his earlier walk.

The man bent over a microscope was not unassuming. His posture, even in the depths of his experiment was perfectly straight, his hair neat in its messiness and his suit obviously hand tailored. Despite the obvious wealth nothing stood out to John as particularly bizarre or remarkable.

"Mike, can I borrow your phone? There's no signal on mine." His voice was unusual, John allowed. A far deeper timbre than was common sung from his throat but it wasn't until John offered his own phone after Mikes refusal to the man that he finally realised what his friend had been talking about. Their gaze met for a split second as John gave him his mobile and by the slight widening of both men's eyes neither had expected what they had seen.

His eyes were melted mercury, swimming grays and greens. They made no sense. Of course all humans had a swirl of colours, background emotions that tossed and changed, but there was dominance, splotches of strong emotions. This man, his eyes were a hurricane of muted colours, nothing stood out and nothing could be read.

"Afghanistan or Iraq?" The stranger asked.

"Sorry, what?" John was more than a little floored by the question. Before he could register however, the man was speaking again.

"How do you feel about the violin?"

John couldn't help but repeat himself. "I'm sorry, what?"

"I play the violin when I'm thinking. Sometimes I don't talk for days on end." The man glanced at him. "Would that bother you? Potential flatmates should know the worst about each other. Got my eye on a nice little place in central London. Together we ought to be able to afford it." He spoke quickly, no words wasted, as he handed John his phone back and shrugged on his coat. "We'll meet there tomorrow evening; seven o'clock. Sorry – got to dash. I think I left my riding crop in the mortuary."

John bristled.

"Is that it?"

"Is that what?" His eyes widened innocently and John felt a mix of exasperation and amusement.

"We've only just met, and now we're going to go look at a flat?"

"Problem?" He was smirking, John began to suspect the wide-eyed innocence was just an act.

"We don't know a thing about each other; I don't know where we're meeting; I don't even know your name."

His eyes flashed and it was only when he stepped closer to John that he refocused on the impossible irises.

"I know you're an Army doctor and you've been invalided home from Afghanistan. I know that your therapist thinks your limp's psychosomatic – quite correctly, I'm afraid. I know you're a brave man who is bored of civilian life and I know that in the time we've been talking shades of pink have appeared in your upper irises. That's quite enough to be going on with don't you think?"

Before John could react - not that he thought in that moment that he could - the man had swept out of the room.

"Oh." The curls reappeared briefly. "The name is Sherlock Holmes and the address is 221B Baker Street. Afternoon." With a wink that those eyes made alluring even if that hadn't been Holmes' intention, he left as quickly as he reappeared giving John the impression he had just been winded two feet from the finish line.

He didn't speak for a moment, but when he recovered himself well enough, he looked in the nearest glass cabinet. He was almost pressing his nose against it before he could see the pink Sherlock Holmes had been talking about - tiny and barely visible dots. Mike cleared his throat and John, chuckling with embarrassment straightened up.

"Yeah," said Mike, "he's always like that."

John still wasn't sure if he wanted to be there even as he stepped out of the taxi to see Sherlock Holmes standing in the doorway.

"Ah, Mr Holmes."

"Sherlock, please."

The shook hands and avoided eye contact. John wanted to see those eyes again with a craving that not quite scratched the surface of consciousness. As instinct so often does with humans though, it won out and John looked at Sherlock's nose instead.

The flat and the landlady seemed equally bizarre and pleasing, although the mess left something to be desired. The pink streaks of curiosity that had remained part of Johns appearance since his first meeting with Sherlock were only aided by the fact he had no clue what to make of this man. The mess that John soon discovered was Sherlock's own only added to the unconventional portrait he had been involuntarily creating.

"Oh go on, I know you're dying to ask." Sherlock interrupted his internal musings.

"What? I-" John was visibly startled.

"Oh don't be so obvious." Sherlock scorned and flung up a hand impatiently. "The eyes! I know you're curious, everybody always is. People are so dull." He spoke quickly and although John was unwillingly to admit it, he was getting more interested in this eccentric man by the moment.

"Yes alright," he allowed. "I'm a doctor for God's sake, of course I want to know."

"Genetic mutation." Sherlock waved his hand again before stuffing both in his suit pockets. John was forcefully reminded of a sulking child. "Boring. Doctors were fascinated of course. To my knowledge - and my knowledge is superior - I am the only known human with this condition in the living world."

As Sherlock had been speaking John had sat down to avoid leaning on his cane and now looked at him with interest. "But, and I don't mean to be rude, but what exactly is the mutation? And how haven't I heard of you?"

Sherlock was still half turned to the window but he smirked at the second question.

"Unlike the rest of the human race I remain an enigma. My eyes are merely colours, they flicker and change but not in any way like the bright colours you're acclimatised to. High-functioning sociopath. My emotions remain hidden."

"But that's amazing." John blurted. He chose to step over the sociopath comment for now. "Absolutely brilliant! They look-I mean, you look-" he faltered. In truth Sherlock's eyes were incredibly enticing, not being able to understand the obviously brilliant brain behind them only added to their mysteriousness. He swallowed, a bit not good to be so enraptured by someone he just met.

"That's not what people usually say." Sherlock had turned to regard him. John wasn't used to reading faces but he could have sworn that mixed in with mild surprise he saw a flash of something more open.

"What do they usually say?" John wasn't sure he wanted to know the answer.

"Unimportant." Sherlock muttered.