Sherlock had suspected something. Not at first, he ignored it, because the symptoms were so minor and really, he ignored anything related to his transport unless it was completely debilitating.
Really. They were so minor. They could have been anything. Even John, if he had told him, would have dismissed it as something inconsequential, like a virus or a bacterial infection.
But when it got to the point where the symptoms were interfering with his work (although still not to the point where John noticed) he realized something was definitely the matter.
So he went to the lab. Shooed Molly out. Borrowed equipment. Did tests.
Got results. Needed to do further tests.
Called John. Told him he wouldn't be home tonight, not till tomorrow.
Snuck into the MRI machine at 3 in the morning.
Got results. Needed to do further tests.
Pleaded and begged Molly to do a spinal tap. Talked her through it. Hurt like hell.
Ran tests. Waited.
And by morning, he knew.
For one of the only times in his life, Sherlock was truly horrified.
(When John was wearing the bomb. When he saw the hound and couldn't explain it away. And when he stood on the roof and looked down at John, knowing how much it would break him and yet, knowing if he didn't that everyone he cared for would die.)
And now.
He wasn't sure what happened after that. It was a bit of a blur. Rather like... shock, he supposed. Shock with no blanket.
He didn't make it home that night. He only knew that because when he did find himself at home, must have been the next day, John was livid. But he couldn't face John yet.
Muttered something about an experiment and a pounding headache, which was true. Side effect of the spinal tap.
John probably saw something in Sherlock, saw that this was true. He waited to yell at him till the next day, because Sherlock slept for almost 20 hours. (Right there, John should have noticed something was wrong. But he didn't. And Sherlock was both thankful and infuriated for that.)
He took the yelling. Felt bad. Told John he was sorry.
And he really, truly was. Just not for the reasons John believed.
But there would be time for that later.
But not too much later.
John worked that day.
While he was at the surgery, Sherlock did research. Extremely depressing research. He only learned things that he already knew, having fleetingly shown an interest in it years ago and never getting around to deleting it.
But this time it was different.
Because he was looking at his future in painful detail. These weren't just symptoms anymore, these were what his life would turn into. Not just a time line, but a countdown.
Everything was there, horrifying, in black and white painfully clear details.
He almost wanted to destroy his laptop. Or the internet. The world.
Everything.
He settled for sulking for the next couple of days.
John assumed it was because of the lack of interesting cases. Mrs Hudson tried to cheer him up, telling him it would only be a matter of time before a nice murder turned up.
He tried to smile and nod, but they had no clue.
By the end of the week he was sick of sulking. He accepted the very dull case Lestrade brought him (only a four at the most) and solved it in less than a day, even going so far as to chase the killer down, John in tow.
After all, he might as well enjoy it while he still could.
He didn't know how much longer he would be able to work for. The initial symptoms, most notably memory lapses, would only get worse and physical symptoms would soon begin to show.
That was probably the worst part.
Because out of all the research, there was one phrase that stood out in his mind and wouldn't go away, no matter how many times he tried to delete it.
It was a month later that the shock wore off. It was as if there had been wax paper blocking his vision and when it was peeled off, Sherlock could see that it was time to tell John. Especially now that the first physical symptoms were beginning to manifest. He couldn't hide those from John.
He knew it would be the hardest thing he'd ever have to do.
Except for perhaps... that.
"John," he began one day. It was sunny that morning, and John had opened the curtains, insisting that it was healthy for Sherlock to get the occasion ray. He was lying on the sofa curled up, back to the sun, secretly enjoying how the sun warmed him.
"Sherlock," John replied, noting with a smile how much Sherlock looked like a cat in that instant.
Sherlock rolled over slowly, knowing that no matter how many more times he rehearsed this conversation in his mind, that it would not be any easier.
He didn't speak for a moment, and that silence spoke volumes to John, who carefully folded up the newspaper he was reading and laid it on the table.
"John," he hesitated, hating that he had to say it, "I'm going to die."
John examined his face carefully, not entirely sure of the expected response.
"Well, yeah Sherlock. Everyone's going to die."
Sherlock shook his head softly.
"I have 6 months. Maybe more. Probably less."
John forgot how to breathe for a moment. For a lifetime. When he did recall, he took a shaky breath.
"How?..."
Sherlock looked over at him.
With pity, John realized. He's the one dying and he's looking at me with pity. "Creutzfeldt-Jakob disease," he said slowly, avoiding John's stare. "The sporadic form."
He looked him in the eye briefly. "Heard of it?"
John only continued to stare at him. Blankly.
Sherlock waited, seeing the shock on his face.
John didn't know how long they sat there for, probably only seconds, a minute at most, but it seemed to be lifetimes and a single heartbeat all at once.
He nodded, surprised that his body was still listening to his brain.
"Some," he managed.
"I have some reading material prepared for you," he said carefully. "If you'd like."
"How long have you known?" John heard his own voice and was shocked by it. And at the same time, a bit frightened. He didn't recognize it all low and growling and demanding.
Sherlock flinched slightly.
"About a month," he whispered.
John slumped in his chair.
After an eternity he spoke, barely loud enough for either himself or Sherlock to hear.
"All right. All right. I'll go make some tea and you can get that reading material for me," he paused to take a shaky breath, "and then we can talk about this."
He got up without waiting for Sherlock's answer, and began unsteadily towards the kitchen.
Sherlock watched him go, feeling something that he recognized as shame, but had no idea why.