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John came back from the clinic one day to find Sherlock sitting at the kitchen table, sleeves rolled up to the elbows, staring at a heart in a petri dish. His hands were pressed gently together, the tips of his fingers resting beneath his chin, and his brilliantly coloured eyes gazed almost serenely at the heart, sitting in a nest-like tangle of wires and batteries.
“…Do I even want to know?” John asked eventually, unfreezing from his spot beneath the archway leading to the kitchen and walking slowly over to the kettle and tin of teabags, keeping one eye on Sherlock and whatever insane experiment he was conducting as he did so. Sherlock was silent for a few moments before responding, his voice a soft murmur.
“Mm, probably not. It’s a human heart, if you’re interested,” he added, causing John to pause, frown and then look away.
“Is that even legal?” he asked, filling the kettle and setting it to boil as he found two (relatively) clean mugs. Sherlock gave a shrug in response, which John half-glimpsed from the corner of his eye.
“Does it matter? I got it from the morgue – I’m sure Mycroft will sort out any problems, if they arise.”
“Right. Ok. And I’m sure I should just stay perfectly calm because there’s a human heart in the kitchen. An actual, human heart.” John paused to shake his head, turning around to look at Sherlock’s back, one mug still held in his right hand. “Why do you need a human heart? And what’s all the…” he waved his free hand at the tangle of wires, assuming that Sherlock would know what he was talking about, “…stuff for?”
Sherlock lowered his hands, standing up and turning around to lean back against the table, flicking a small switch on a black box as he did so. “I’m measuring the distance variations of cardiac muscle at different beat speeds,” he replied with an exasperated sigh, gesturing behind him to the array of batteries, “Clearly, a living human heart would be much better, but for now I’m stuck with using an old one and alternating electrical currents.” He turned his head to one side slightly, frowning in annoyance. “It’s not perfect, but it’ll have to do. I can’t exactly go up to people and just ask to listen to their hearts.”
“You could listen to your own,” John suggested, hearing the kettle roar, quiet and click behind him as the water finished boiling, quickly pouring it into the mugs and reaching for the sugar. “I’m still a doctor, Sherlock – I’ve got a stethoscope in my room.”
He turned back just in time to see Sherlock roll his eyes, leaving the tea to steep on the counter behind him. “Yes, I know you have,” Sherlock replied, “But it wouldn’t work if I measured my own heartbeat. I need a volunteer, a specimen!” He almost snarled as he finished speaking, baring his teeth in a frustrated grimace and slapping one hand down on the table.
“I-…right, ok,” John replied, feeling more than a little confused. “Couldn’t you ask Mrs Hudson?”
Sherlock shook his head, sending his dark brown curls flying and bouncing. “These results need to be for an average individual – average age, weight, fitness. Obviously some variation is to be expected, but Mrs Hudson is too far above average age to be of any use to me.”
John nodded slowly, absently turning back to the tea and removing the tea bags, pouring in the perfect amount of milk before offering one mug to Sherlock. Sherlock took it in silence, their fingers lightly brushing as he did so, and then wrapped both pale hands around it, lifting it to his lips to take a small sip. A slight smile spread over his face as the first drops were consumed, and he lifted his head to give John a slight nod of approval – the best ‘thank you’ John would probably ever get for making him tea.
The two stood in silence for a while, quietly sipping, before John finally broke the silence.
“What about me?” he asked. Sherlock frowned at him slightly over his mug, putting it down to one side and staring at him once he had drunk.
“I beg your pardon?”
“What about me?” John repeated, “I’m probably one of the few ‘average’ people you know, and I really doubt Donovan or Anderson would let you listen to their hearts.” Sherlock’s mouth pulled up and to one side in a displeased, almost disgusted, grimace as John mentioned the two Yarders, and John chuckled quietly. “See? Face it, when it comes to measuring human heartbeats – for whatever reason – I’m probably your best bet.”
Sherlock was silent for a little longer, placing his mug down next to him (narrowly avoiding a lump of wires) once he had finished with it and staring at John, before finally giving a short nod. John grinned, finishing his own tea and dumping the mug in the sink before starting to walk over to his room. “Excellent! You plonk yourself down on the sofa, I’ll go get my stethoscope.”
He hurried off before Sherlock could respond, and shook his head in amazement at his own actions once he was safely out of sight. Things really had changed for him after meeting Sherlock – he had just come home to find his flatmate with a human heart for Christ’s sake, and instead of admonishing him or calling the police or anything, he had made him tea and then offered to be a substitute.
A substitute for a human heart, he thought as he rummaged through his drawers, eventually finding the stethoscope, what has happened to my life?
He headed back downstairs to find Sherlock sitting on the sofa as he requested and held out the stethoscope, waiting for Sherlock to take it before he sat down next to him, pulling off his jumper to leave just a shirt between the stethoscope and his skin. Sherlock nodded his thanks once again, slipping the earpieces into his ears with practised hands, only to freeze with the end of the stethoscope an inch away from John’s chest.
“Are…you sure this is ok?” he asked quietly, face creased with concern as he turned his full attention to John. John just nodded and smiled, taking Sherlock’s hand and gently pressing the end of the stethoscope to his chest, letting it rest over his heart. Sherlock smiled warmly, an action that somehow filled John with warmth, his eyes sliding shut as the steady thump of John’s heart echoed through his head. Slowly, very slowly, Sherlock shifted closer to John, first lifting his legs to curl them up on the sofa beneath him, and then leaning forwards to carefully rest the side of his head on John’s chest, just beside the end of the stethoscope, giving a very slight (and almost possibly unintentional) nuzzle as he did so. John had to stifle a chuckle at that – Sherlock was almost acting like a giant kitten. On impulse, he lifted one hand, gently starting to stroke the top of Sherlock’s head – in response, Sherlock smiled, giving a contented hum and giving John’s chest another nuzzle, fingers flexing slightly under John’s hand.
“Look at you,” John murmured, continuing to run his fingers through Sherlock’s thick hair, “You’re just like a kitten.” Sherlock frowned but didn’t move, curling his other hand into John’s shirt before replying.
“’M not. This position just happens to let me listen to your heartbeat as well as possible whilst also being rather comfortable for both parties involved.”
John actually did chuckle at that, wrapping his hand tighter over Sherlock’s. “Sure, you just keep telling yourself that.” Sherlock frowned again and muttered to himself but didn’t move from where he was, only shuffling in place slightly to better curl up next to – and partially on – John.
It took him a long time to realise that the genius had dropped off to sleep, listening to the comforting sound of John’s heartbeat.