Sherlock's ears pricked at the faint stumble from upstairs. John's room, he mused, sitting bolt upright in his armchair. He listened to the soft pad of feet down the staircase, the sounds slightly hesitant, unstable, like John was finding it difficult to co-ordinate himself. A few seconds later the little man appeared in the living room, his blond head in his hands.
Sherlock's heart went out to him. He rushed over, pressed guiding hands to his flatmate's shoulders and helped him onto his armchair. John's face was screwed up in pain, and he had to bite back a whimper after slumping a little too quickly to his seat. He felt softer, thinner, under Sherlock's fingers.
It was like he was wasting away.
"I see the headache is back," Sherlock observed. John started to nod, then winced and stopped.
"I feel awful," he said in a frighteningly small voice.
Sherlock petted him for a bit, massaging John's shoulders, the nape of his neck, until the man had softened into the armchair with little moans of appreciation. He gently threaded his fingers through the fine strands of John's hair, letting it slip over his fingers like gold threads. John had his eyes shut, his head in Sherlock's hands, eyelids flickering as he was trapped between pleasure and pain. Sherlock, for a moment, admired the long smudge of lashes resting against cheeks.
"I'll get your medicine," he said, once he was bored.
John was always appreciative of even the tiniest scraps of affection.
Sherlock swept to the kitchen and opened the doors to his steadily increasing medicine cabinet. John had been ill for near a month, and Sherlock's stock of medicines had only gotten bigger. He popped two sugar pills from a packet of Nuramol, and grabbed the bottle for head cold mixture that John had asked him to pick up from the pharmacy. With a glass of water and a desert spoon, he returned to his patient.
John struggled upright as he approached, mouth tightening with every jerky movement. Sherlock knelt beside him, a hand at his back to help keep him steady, and John leant gratefully with him, letting out little gasps.
"Open your mouth," Sherlock said quietly, and when John acquiesced he placed the sugar pills on his tongue, little white tablets on soft pink muscle. John's eyelashes fluttered, blue-grey eyes gazing at him. Sherlock held up the water. "Drink."
Sherlock didn't know whether to thank the army for John's instinct to follow orders when said in a certain tone, or whether to thank genetics. But it was like feeding a kitten. John obediently swallowed the water in long gulps, his throat working fast to keep up as Sherlock tilted the cup a little too quickly. Water spilt over his chin, and he spluttered, sweetly red with embarrassment.
"I'm sorry." He sounded horrified by his own weakness, his inability to even drink a cup of water without making a mess.
Sherlock soothed him. "Don't be sorry, John. It's not your fault."
He poured a spoonful of what John thought was head cold medicine, and brought it to John's mouth. A slight pressure of stainless steel against the soft flesh of his bottom lip, and John's mouth clasped over the cold metal. Sherlock watched him swallow.
He remembered when John first got ill.
John had caught it off Sherlock, who had managed to fight it off without much fuss, but the illness hit John harder. From then on, the flat was polluted by the noise of John coughing and spluttering and generally being disgusting background noise to Sherlock's experiments. John insisted on doing the shopping, the tidying, and continued typing determinedly on his blog in the lounge as Sherlock grew steadily more furious at each hacking cough. He'd have happily done more chores if it meant John could go noisily recover somewhere else.
It was when the vicious headaches kicked in that Sherlock started getting interested.
John physically couldn't stomp around and make a nuisance of himself when he was in pain every time he blinked. Headaches rendered John smaller, quieter, less argumentative and more grateful for Sherlock's attention. He slowly grew dependent on Sherlock, and Sherlock had the rare opportunity to find out just how deeply John trusted him.
He'd never had so much control over another human being before.
Using his contacts in the pharmaceutical industry, Sherlock managed to obtain placebo versions of various medicines, and stocked the shelves with them whenever John asked him to buy something. A steadily weakening John took them himself without even realising what was wrong. The thought wouldn't even have crossed his little mind.
After helping John mop the water off his shirt, Sherlock assisted him back upstairs. John's brows furrowed as he concentrated hard on placing his feet, resting some of his weight on Sherlock's hands. The shapes of his back felt so comfortable, so warm. Sherlock just wanted to cling to him, even as John trembled in pain. It was difficult to restrain the impulse.
He helped John lie down in his bed, moving slowly so as not to irritate his headache. John sighed as he finally rested against the pillows, smiling weakly up at Sherlock with honest gratitude. Sherlock glanced over his kind face, and perched on the edge of the bed next to him, pressing the back of his hand over John's forehead.
"The fever's gone."
Sherlock was oddly disappointed.
John blinked up at him from under Sherlock's hand, oblivious as ever. "Yeah," he said, with a small smile. "I think I'm finally getting better."
Sherlock had liked the fever.
He remembered it well. A small, shaking John splayed out on his back, murmuring in pleasure as Sherlock gently pressed a cool flannel over his forehead, trusting eyes gazing blearily up at him with so much gratitude that Sherlock felt like the most important person in the world. He was so vulnerable like that. So malleable to Sherlock's whims.
Sherlock had always adored John, and wanted desperately to show it, but John never let Sherlock look after him before. He was stubborn, self-sufficient, and hated even the thought of having to rely on another human being. Doctors made the worst patients.
As John's eyes flickered shut to fall into dreamless sleep, Sherlock waited, watching. Illness had done much for John's character. Sherlock realised, with a faint stab of regret, that he couldn't let John get better. This John, the sick one, the one who had handed over care of his body into Sherlock's hands without a second thought, he was perfect.
With a final brush of his fingers through John's soft hair, he stood, and left to make a phone call.
A few days later, after obediently swallowing his painkillers, John was violently sick.
Sherlock found him on his knees, crouched over in the bathroom, emptying the scant contents of his stomach into the loo. He was crying, and shaking, and when Sherlock appeared he visibly reacted in panic and embarrassment and squirmed pitifully against the cold tiles. Sherlock knelt beside him, rubbing at his back as John retched pathetically, shushing any half-formed complaints. John's skin prickled with cold sweat. It clung to his skin in clear beads at the back of his neck.
"I thought I was getting better," John whispered, voice hoarse.
His eyes were wet with tears. Sherlock got him some tissue paper, and after helping John to his feet, spent the next few minutes standing behind him at the mirror as John self-consciously dabbed at his face until he deemed himself presentable. Sherlock thought he looked adorable. He scratched his fingers over John's ear, and John leaned into the touch, his eyelids dipping close.
His new hobby was too easy.
Sherlock knew the functions of John's body intimately now, vaccinating himself and then timing the introduction of new diseases so that John never fully recovered. He never let John slip too deeply into illness either. He was so weak that he could die if Sherlock overdid it. And that was rather beside the point.
It got to the point where he was ignoring potential cases in order to further his experiments with John, whose steady deterioration was far more interesting than murders. John's simple trust in everything Sherlock did was a marvel in itself. As the evidence mounted up, John seemed to remain oblivious.
One evening, Sherlock had John leaning next to him on the couch. He'd shut the curtains and turned off all the lights, and in the semi-darkness they listened to classical music on the gramophone. The music was for Sherlock, the darkness was for John. His latest disease induced painful photosensitivity.
"I need to go to the hospital."
Sherlock glanced at him, distracted by the key change. "Hm?"
"I've been ill for way too long. I might have something serious. I might have cancer."
Sherlock let out a calculated sigh. "You don't have cancer."
"This isn't normal, Sherlock."
He sounded upset, and a little bit frightened. His eyes glimmered in the dim light, staring at Sherlock with a look that wasn't exactly an accusation, but Sherlock could see that John was starting to get suspicious. Perhaps he'd been suspicious for a while, but thought the idea too ludicrous to bring up.
Sherlock's mind, meanwhile, was running at a million miles a minute. He thought of an unbiased doctor, with an outsider's perspective, picking up signs of different diseases and deducing what John could not and would not see. Sherlock didn't want lose John's trust, however misplaced it was. It meant too much to him.
"I'll sort it out," he said simply, and rubbed at John's shoulder. John's eyes flicked down to his hand, then back up again.
"I can do it."
Sherlock changed tact, softening his voice in a way that always brought John over to his point of view. "I want to help you," he said earnestly.
The hardness in John's eyes faded as quickly as it had come, and after a pause he pressed his small hand over Sherlock's. He was so warm, so gentle, like this.
As the music came to a crescendo, Sherlock leant forward in the darkness, kissed John's forehead, then his lips, like there was no more significance in such a gesture. John huffed and moved back. His eyes were wide, darting over Sherlock's face, searching for the trick.
Sherlock kissed him again, more forcefully this time. He crowded John against the sofa, cupped the back of his scalp and sucked at thin lips that gulped down air and kissed back with a nervous tremor. It was like he was afraid he'd wake up.
He pulled away, and Sherlock stared down at him, practically in John's lap. John looked terrified, exhilarated. "I thought you didn't-"
"I don't," Sherlock interrupted. "Usually. But you're different."
John smiled widely at him, and stroked his fingers down Sherlock's cheek.
The next day, Sherlock arranged for John to meet a doctor.
Dr Trevor owed Sherlock his life, and he acted his part as the consummate professional, visiting the currently delicate John at their flat to look over him. He took samples and gave John a thorough physical as they laughed over stories about medical school. John looked hopeful for the rest of the day. He came to Sherlock, who was in the kitchen looking over various bacteria samples, and kissed him deeply before going to bed.
"Thank you," John said with a shy smile, so close that Sherlock had to do his very best not to grab him and do something terrible.
"It's not a problem," he said instead, and watched John's slow shuffle out of the room on bare feet.
He went to Victor Trevor to collect the fabricated results. The doctor was obviously conflicted, dithering over everything so much that Sherlock wanted to slap him.
"Are you sure about this, Sherlock?"
Sherlock treated the man to his best grin. "When am I ever unsure of anything?"
Victor looked dubious, but he handed over the results all the same. "If it comes out that I've been a part of this-" he said loudly, an attempt at bravado, but Sherlock interrupted him.
"It won't come out," Sherlock said shortly, snapping the folder shut with a thin smile.
He went back home, to John.
Silently, he crept up the well trod path to John's room, depositing his coat over the stair rail and pushing open the door into the dim bedroom. John was on his bed, where Sherlock left him. He'd torn off his pyjamas in a hot flush and lay whimpering in twisted sheets, clutching at his stomach with clenched fingers. He was in agony.
Those deep eyes, pleading.
Sherlock sprung into action like a paramedic. He fed John his useless pills, soothed him, cooled him down with a wet flannel that he pressed with tender care over John's sweaty forehead. John looked delirious, like he was looking at the world from a slightly different angle. He seemed to take a while to react to anything, and he was trembling so hard that he almost vibrated against Sherlock's fingers.
"You're freezing," Sherlock said, worried.
John seized his hand, distressed, his fingers slippy with sweat. "It hurts," he sobbed. "Sherlock, please."
He sounded, broken.
Sherlock peeled back the sheets and slid in next to his John, scooping the shuddering body into his arms and letting John clutch at him with a worryingly frail grip. His head twisted on the pillows, his ears and cheeks flushed red as he panted loudly in the dark. Sherlock leant closer, his lips brushing John's sweaty hair.
"I've got you."
John shook harder, and Sherlock squeezed their entwined fingers.
"I'll always have you."