As much as John hated to put Sherlock in the line of fire, he was their best defense. In the chaos of the city, he was able to spot the small disturbances amid the debris since the last time they'd been to the area as they searched for supplies and avoided both the zombies and the scavengers that would kill them for their supplies.

They'd taken refuge in the hospital, knowing that they couldn't stay at the flat. Despite two months of research and testing, they were no closer to finding a cure or a way to stop it. There wasn't even a clear reason for it, the theories nothing more than and none able to be proven.

The hospital couldn't offer them everything though, and it was on a supply run that everything changed. They'd been too confident, too sure of themselves, not having encountered anything in days, so of course that's when everything went wrong.

"Sherlock," John yelled, seeing movement and raising his gun. But it was too late.

Before Sherlock could even make a sound, the creature was on him, blood gushing as his throat was torn out by ragged teeth.

John emptied the cartridge into the creature which shrieked and tried to scurry away but Neil was ready with the fire bomb. Bile rose in John's throat as his eyes took in the wound and the black blood that was already concealing at its edges. Neil had another Molotov cocktail ready, knowing full well the protocol they'd set in place when this happened, but John's hand on his wrist stilled him.

"John," Neil protested.

"No," John growled. "We're bringing him back with us."

"But—"

"No!" It wasn't a shout, his voice barely raised, but it was the tone of voice that soldiers knew better to disobey and Neil was a good one. John moved forward towards Sherlock who still laid prone, sprawled against the ground, eyes wide with shock as his hands grasped at his ruined throat.

Shaking his head at John's advance, Sherlock scuttled backwards.

Saying a prayer to the higher powers if they were still listening, John begged for forgiveness as he brought the butt of his gun down on Sherlock's head.

John hadn't had any plan when he'd had the men bring Sherlock back with them. There had been protest when he had Sherlock locked in one of the labs they didn't use instead of the ward they normally housed the creatures in when they captured one to study and test.

John wasn't sure how long he watched Sherlock's still form where it laid on the counter through the reinforced glass that separated them before Sherlock finally awoke. It was like any other time Sherlock woke up: one moment he was sleeping and the next he was completely awake. But John could see the difference right away despite the obvious fact that he was still alive and that the wound had instantly clotted from the infection.

John's throat felt thick as he watched Sherlock's trembling fingers reach up to press at the gaping wound before pulling away with a start and turning with a wrench to lock eyes with John. The pain, and desperation, and outright fear that his face held as he met John's eyes, cut right through him. Closing the distance between them, Sherlock banged on the window, causing John to jump. "Why?" Sherlock mouthed silently, but John just shook his head jerkily, unwilling to say that he was a selfish bastard and couldn't do the right thing and put his lover out of his misery.

Raising his hand, John pressed it against the glass separated them, his heart in his throat as Sherlock mirrored him with a shaky hand. Closing his eyes against the rush of tears, John turned and walked away, not stopping at the sound of the banging on the window or the sound of glass breaking as Sherlock destroyed the lab.

No one tried to stop him or talk to him as he raided their stash of liquor, didn't stop him as he tried to drink the memory of the day away and pretend that Sherlock would be next to him when he woke up instead of a dead man walking. It didn't work however, and despite waking up with a killer hangover, John's first thought was of Sherlock, and he sobbed brokenly as he was sick in a bucket.

Sometime later Molly came in, worried, and John yelled, throwing an empty bottle at her where it shattered dangerously close to her head. Molly's fear brought John back to himself, and he found himself apologizing. Molly shushed him, and pulled him close, and John lost himself to the sorrow again, crying until he was sick with it, until his head ached and his eyes burned, and still he clutched at Molly desperately. He had to be hurting her, but she didn't complain, just soothed him, held him as he fell apart.

Finally, when the tears had run out, Molly pulled him towards the shower, and he followed meekly, not even feeling embarrassed as she helped him out of his clothes and into the warm rush of water. Molly left as he cleaned himself, but he found fresh clothing laid out, and vowed to get her something good on their next supply run.

Making his way to the mess, John was almost run over by Neil. "Sir, you've got to see this."

John couldn't even ask what he meant before he was being pulled along. Dread built in his stomach as he realized that they were heading towards the lab that Sherlock had been locked in, and John was ready to dig his heels in, not wanting to see the creature that had replaced Sherlock. But Neil outweighed him by a good four stones, all of it muscle, and John didn't have much of a choice. The crowd gathered around the window was a shock, but John had no idea what to imagine.

He certainly hadn't expected to see Sherlock working in the lab as he always had. The other doctors were abuzz with speculation, but John's mind was blank, not understanding. And then John was laughing hysterically, losing it as he realized that this must be some sort of cosmic joke and it was all on him. Sherlock froze for a moment at the sound, the only indication that he was even aware of the people watching him.

Days passed and the other doctors eventually returned to their work as Sherlock kept up his own, an endless vigil broken only by supply lists written on the window. They never could figure out why Sherlock didn't deteriorate like the other zombies, hypothesizing that it had happened to others, they just hadn't encountered the phenomenon before. Or it could have just been a Sherlock thing; leave it to Sherlock to have a brain that couldn't be conquered. In any other situation, it might have been amusing, but John couldn't find anything to laugh about.

John went through the motions of living, doing what needed to be done, and trying his best not to think about Sherlock, or not-Sherlock, or whatever was now in Sherlock's skin. He lived in a bubble, untouched by the chaos of the world around him, unwilling to face it. The nightmare continued the same way for another two weeks before another commotion broke out, the doctors dashing about in excitement.

"What's going on?" John demanded, stopping the nearest one.

"Sherlock did it; he created an immunization that works on the rats with no apparent side effects. We're going to monitor the rats for another week before trying it on a human," the man said before running off again.

John's thoughts whirled. An immunization, a way to prevent it, but not a cure, not a way to reverse it. John had been hopeful, but knew that that it would be nigh impossible. Hesitantly John went to Sherlock's lab, not sure what he expected to find there, having avoided it as much as he could. Seeing Sherlock standing at the window, John had to force himself to keep moving forward.

Sherlock had changed out of his ruined clothes at some point and donned scrubs, likely only to prevent contamination of his testing. John could almost imagine that this was still Sherlock if he ignored the grey tinge of his skin, the black-edged wound standing out starkly on his throat, and the blankness of his eyes. Sherlock's hand suddenly raised and rested against the window, and John couldn't hold back the sob as he raised his own up to rest on the glass separating them. Somehow there was still a part of him in there, a part of him that recognized John and that was the worst, knowing that Sherlock was trapped in this.

This time when John turned away there was no commotion and that hurt just as badly. John should have been happy, excited by Sherlock's discovery but he couldn't bring himself to care. Distracted as he was, it was no real surprise that he didn't notice the zombie until it was on him, screaming as its teeth sank into his arm as he tried to keep it away.

Neil got it off him and set it ablaze before he and the rest of the men stood apart from him, wary and unsure. John knew that they had every right to be as he could already feel it coursing through his blood, changing him, taking him over. "Take me to Sherlock," he begged, though almost wished they wouldn't. The trip back to the hospital was quiet and John felt his mind slipping away with each step.

Molly was waiting for them when they returned, happy with the news that the immunization had been tested and worked, but trailed off in horror as she saw his wound. "John," she breathed in sorrow. "We can try—"

"No. No. You know it's too late for me. It would be worthless. It's time. Evacuate everyone. Go to Mycroft, he'll take care of the rest," John forced the words out, turning towards Neil. "You're in charge. Keep them safe."

Neil saluted and John couldn't even bring about the normal surge of annoyance at the gesture. Vision suddenly dimming, John gasped, "Sherlock!"

Hands tugged on him, leading, and John didn't fight it, moved mechanically as he held onto the mantra of Sherlock, the word quickly losing meaning, but it was all he had. Suddenly John found himself pushed through a doorway and arms wrapped around him, holding him close as his legs gave out and they both sank to the floor.

"Sherlock," John breathed. Yes. Sherlock.

Sherlock's hands on him, tugging at his clothing, searching. The brief pain as he found the bite.

Sherlock. Who. Yes. Love. Hold.

Sherlock.

Wrapped together, the world exploded around them, their last thoughts of each other.