Title: Poison
Summary: Holmes is poisoned, and Watson mistakes it for cocaine abuse. It's a good time to have a big brother about...
Spoilers: I adapted the (rather peripheral) 'case' from the books (A case of identity).

Dedicated to big brothers everywhere...

Holmes sat staring in fascination at the candle flame on the windowsill, looking pale and sick, as Watson tried to turn his raging guilt to something more productive, miserably reflecting on the day's events, and his failure as a doctor and as a friend.

"I'm sorry Holmes. Why on earth didn't you say anything?" He rubbed tired eyes. "How did Mycroft know?

"Mycroft knows everything." Holmes answered distractedly.

"But how did he know?"

"He knows everything." Holmes repeated ...and Watson remembered that his friend was not currently all there.

"Nobody knows everything" He said with automatic patience.

"No...nobody. Except Mycroft. Did you know he's my brother?" Holmes turned to him looking satisfied. Watson returned his look with unmasked guilt and concern.

"Just try to rest old boy."

"Necesito decirles algo-"

"Holmes, I don't speak Spanish."

"Ah." he looked confused, then said "Ich brauche-"

"Or German."

"Sai'n teimlo yn dda iawn, -"

"I don't even know what language that is, Holmes! Speak English!"

"Oh...I think I'm going to be sick."

Watson grabbed the bin, and sure enough Holmes did expel the entire contents of his stomach, which happened to be not very much.

"Watson!" Holmes exclaimed suddenly, as though he'd only just noticed him. "What are you doing here?"

The doctor tried to reassure himself that it was only temporary as the detective's attention leapt from one thing to the next. Watson rubbed his eyes. He had been called over to the house by a telegram - requiring his medical assistance. He had found Holmes throwing up, with pains in his stomach, shaking, talking nonsense and ... he had thought it was due to Cocaine. That assumption could have cost Holmes his life.

"Is it your birthday Watson?"

"No...it's not my birthday." he said tiredly, but patiently. After all, Holmes was not at fault for his current behaviour.

"I have the strangest feeling I've forgotten something...perhaps it's Mycroft's birthday..."

Watson sighed and looked towards the door, beyond which Mycroft Holmes sat reading the paper. It was only the arrival of Mycroft - who saw not only that his brother had been poisoned, but went a step further - examining the tea cup Holmes had drunk from, using his brother's chemistry kit before rapidly coming up not just with the poison, thallium, but even handing him the antidote, a blue pigment Holmes used for detecting iron called Prussian Blue.

He had administered the antidote as quickly as possibly, tensely aware of the fact that somebody had wanted Holmes to die a slow, painful death.

"Try to drink a little more water, Holmes, you must not become dehydrated." Watson helped him take a few sips of water, praying the shaking in his friend would abate soon. He washed out the bin briefly and returned it to Holmes, finding him lightly asleep.

He left the younger Holmes sleeping to find Mycroft.

"How is he?" Mycroft asked, not looking up from his paper.

"Better...I think. He needs rest, and plenty of liquids. In the meantime whoever did this is still out there..."

"Not for long. Fear not, doctor, I have sent instructions to the police to apprehend the poisoner."

Watson was stunned into silence for a moment. Perhaps Holmes was right, perhaps his brother was simply omniscient. He hesitated.

"Perhaps you could start at the beginning?" he said, trying to get to the bottom of exactly what Mycroft knew about all this. Mycroft put the paper down and looked at the doctor plainly.

"A man tried to poison my brother."

"Yes I understand that - but how did you know?"

"Ah" Mycroft said, as he examined Watson's confused expression. "... you mistakenly believe I knew of this poisoning prior to my arrival. In fact I was coming to see my brother in the matter of a case, and chanced upon the incident. It was, however, my first clue that his illness was not self induced. Sherly uses cocaine for mental stimulation, and morphine to help him sleep - neither of which would be necessary when he was expecting my visit."

"When I was living here, you did not visit more than once every six months." Watson said, sceptically.

"Yes. But you are no longer living here." Mycroft met the doctor's eyes and Watson understood. It wasn't an accusation...just a fact. "I have taken to visiting on a more regular basis."

His questions were interrupted by the sound of vomiting and he dashed back into his patient's room instinctively.

"Watson... don't drink the milk...I fear it has gone off." Holmes got out around the sheer exhaustion of being so ill.

"It's not the milk Holmes, you were poisoned!"

"Poisoned... why is that thing moving?"

"It's a clock hand. Holmes..."

"Yes yes I was poisoned with thallium, you said."

"I didn't say it was thallium."

"Given the facts, it is the only logical choice ... " he yawned and sat back in bed. Watson shook his head at the subconscious genius of his friend even in his current state...though he supposed with a knowledge base like Holmes, the prussian blue was something of a giveaway.

"Don't fight sleep Holmes. You need it." He said.

"You should get some rest too, Watson...it's almost midnight.." Holmes said before drifting off. Watson decided not to correct his friend's misguided assumption that it was 11pm instead of am, and again left the room quietly, after putting both the bin and glass of water in easy reach.

He sat down opposite Mycroft. "What of the poisoner?" he said, getting straight back to business.

"Last week my brother told me of a case that he was drawing to a close. A rather trivial matter involving a woman who had been tricked by her step-father into remaining a single woman so that he could retain access to her wealth. My brother confronted the man... who knew that there would be only one way to prevent his step-daughter learning the truth, which was to kill Sherlock. Murder by poisoning seems rather popular these days..." Mycroft pondered. "In fact, there was a case not long ago-"

"But how did he poison Holmes without him being aware of it?" Watson interrupted.

"That would have been distressingly straightforward Doctor. In your absence, Mrs Hudson has opted to leave my brother's breakfast outside his door rather than venture in, so all a potential poisoner would have to do would be to wait until the breakfast was unguarded and slip in the poison. Thallium is almost completely colourless and odourless. It presents as an everyday stomach virus, and kills in a matter of days."

"And you're sure it is this man? We have proof?"

"Fortunately my position with the British government means the police do not require proof before they follow my instructions. Proof is really more Sherly's area..." he gave a bored sigh.

"But I suppose if it is strictly necessary, the possession of thallium based rat poison and a disguise that Mrs Hudson may recognise from the man in the waiting room this morning...the shoeprints in said room downstairs, and teacup could be classed as evidence."

Watson stood and began pacing up and down.

"Doctor...he will be apprehended and made to confess in no time at all. Try to have some faith in our nation's policing force."

"He would have died." the doctor said suddenly, angrily. "If you hadn't come when you did - if it had been up to me, I would have watched him die."

"Nonsense doctor, your logic may perhaps work a trifle slower than mine - but that's not to say it is non-existant. You would have worked out this mystery in time to save my brother." Mycroft reached over and took the biscuit by Watson's cup of tea, casually munching it.

Watson paused. He didn't know if Mycroft was right or not, didn't know if he wanted to dwell on it. He thought of the effects of the poison on the detective's frame, and how ill-equipped he was to deal with sickness at his present weight.

"He's too thin." he said. The guilt came again from how late he'd been to notice. But somehow, in doctor mode, he suddenly saw how frighteningly fragile his friend looked- and knew it wasn't just the poison-induced sickness. He wasn't eating properly.

"Ah...yes. My brother's eating habits have always been unreliable. I could never understand it..."

Watson sat down restlessly, wishing he had a vent for his frustration.

Mycroft continued, as perceptive as ever. "You cannot be blamed for assuming as you did, Doctor, given the number of times you have found my brother in a poor state as a result of cocaine. What matters now is that you use your medical expertise to aid in his recovery."

"I'm not leaving until he is fully recovered." The doctor said unhesitatingly.

"I was hoping you'd say that, as I have some small errands to run" He stood and collected his things.

"Errands?"

"I must ensure Scotland Yard have captured the right man."

"And what of your faith in our nation's policing force?" Watson said drily, to which Mycroft looked a little sheepish.

"I will be back as soon as possible." he stated, and left.

When Mycroft returned, Sherlock was sleeping fitfully. He took a seat by the bed, opposite the doctor.

"Your errands are complete?"

"Yes. The guilty party has confessed."

Mycroft seemed to be going to say more, but just then Sherlock woke with such a violent start that Watson jumped. The look on his face was one of such haunted terror that the doctor momentarily froze...he had never, in all his years of living and working with Holmes...seen that look on his friend's face before. He had never seen Holmes look truly, deeply terrified and it looked totally foreign. He hoped never to see it again. Shaking himself out of his stupor, he realised that Mycroft was already soothing his brother back to sleep.

"Shh...it's all right brother, you're safe. Everything's fine..."

Watson watched Mycroft gently brush away a stray hair while pulling the sheets up around his brother, all the while reassuring his brother.

"Get some sleep, Watson and I are both here if you need us." He patted his brother's arm gently.

"Watson..." Sherlock whispered shakily.

"Is safe, I assure you."

Those words worked like magic to relax Holmes, and he swiftly fell back asleep. When he was once again asleep, this time more restfully, Watson spoke.

"You are more loyal to Holmes than I ever suspected."

"He's my brother." Mycroft responded, easily.

Watson scoffed. "I have a brother I haven't seen in 15 years."

Mycroft continued staring at his brother's weakened form. He started speaking slowly.

"Before my brother came into this world, I was alone with average, slow-witted companions, dull teachers and distant parents."

Mycroft smiled as though despite himself. "As you can well imagine, Sherlock livened things up considerably. He was born with a knack for finding adventure and stimulation...and yes, trouble, ...but here finally was a person of my own calibre to interact with. He proved to be the only childhood companion worth my time, more intelligent at the age of 4 than my 11 year old peers... "

He had Watson's full attention. The younger Holmes never, ever spoke of his childhood. The doctor imagined both Holmes brothers in their childhood years and found he could easily imagine the bored, under-challenged Mycroft, the boisterous mischief-making Sherlock and the vague, distant parents who left them to their own devices.

"Sherlock entered the world with a big brother already firmly established, he has always had that security." Mycroft smiled slightly. "He also entered the world with an almost unnatural amount of energy which I have often wondered at. For me, merely observing his antics from afar has always been sufficiently exhausting... no one has caused me greater concern, more continuous worry, no greater challenge has presented itself than maintaining my brother's welfare...and yet, it was his enthusiasm for life that dispersed all seeds of cynicism in me. I should have been quite a different person save for his influence."

The glaze lifted from his eyes as he realised he had been thinking out loud and laughed in slight embarrassment.

"My apologies doctor... I'm being most intolerably dull."

"Far from it." Watson was quick to reassure. "I understand." ...And he did. When he had come back from the war he'd felt like an old man. A jaded veteran of the horrors of war, an outsider...and then he'd moved in with an eccentric, mercurial, charismatic, infuriating genius who effortlessly brought him back to life.

He was going to say more, but when he looked up again he saw that Mycroft had dozed off. He couldn't resist the opportunity to stare at them both, trying to identify likenesses and differences, first in looks, then in personality. They both behaved as though they lived in a totally different universe from everyone else. He supposed they probably did...but the contrasts between them were striking. Sherlock, with a mind that was constantly ablaze, absorbing information and calculating nonstop... and Mycroft the reluctant genius - using his intellect more by default than by design. He wondered if they understood each other more clearly than he ever would.

He hadn't intended to fall asleep but his doctor instincts were intact nevertheless- waking, as he did, with the first signs of stirring from his patient. Mycroft was still dozing. Watson retrieved a glass of water from the bedside table in readiness.

"Watson." Holmes said, voice only slightly raspy. He took a sip or two of the offered water. "I see you have impeccable timing as ever."

Watson sighed a mixture of frustration and relief. It seemed the detective was back in his own mind again. Holmes's words woke his brother who sat up.

"Ah, brother, you appear to have improved considerably." He stood up. "I shall take my leave - I do hope the next visit will be less exhausting, Sherly- I'm not as young as I once was." he said.

"I suppose Mr. Harwood is behind bars?" the detective enquired.

"You suppose correctly. Good day brother."

"Good day."

Watson wondered at the formality the brothers treated each other with, despite the underlying mutual affection and admiration. Looks could be deceiving... he thought miserably, a stab of guilt hitting him once more. Mycroft left and Holmes immediately attempted to get up - but Watson had a confident authority over him in all medical matters.

"Holmes you are not fully recovered - as you are well aware." Watson knew he must be concealing the aches and pains he felt, as well as the lingering nausea. "You must rest."

Holmes sighed impatiently. Watson almost missed the pliant, delirious Holmes of the night before. But not quite. It was a battle, but Watson won - Holmes would stay in bed for the day. He sat with him and they had a companionable breakfast.

"Holmes."

"Mm?" Holmes said, distractedly reading the morning post.

"I owe you an apology."

"Don't be ridiculous Watson." Holmes dismissed without looking up, then continued "Listen to this - a most intriguing letter! Dear Mr. Holmes..." Holmes read out the letter. Watson shook his head in despair at his friend, then surrendered, and listened attentively to the next case...