John figured it out.

Sherlock had gone through arduous trouble to keep his birthday hidden from John. His birth certificate and other documents were in a safety deposit box across London; he bought Mycroft a new umbrella in exchange for silence. His driver's license never left his body, and when he slept, he hid it somewhere new every night.

But here they were, February 26th, and Sherlock's birthday was tomorrow. John had only found out a few months before, when he'd paid someone to intentionally anger the detective.

"I'm a proper genius, too."

"I doubt it. How do you know John?"

"We were in Afghanistan together. I can prove it, if you'd like."

"I can tell by your stance that you've been to the Middle East."

"No, that I'm a proper genius."

"Fine. Show me."

"Your birthday is in June. Am I wrong?"

Sherlock's smirk was defined and his head was held high as he pulled out his license and revealed the true date. He gave John the silent treatment for four days when he realized he'd been tricked.

"Are you excited?" John asked, looking at his watch. The birthday was only nine hours away.

"I do wish you'd call it off."

"You're going to learn how to enjoy this, Sherlock, even if it kills you."

Sherlock scowled and sat in his chair. "At least tell me what you've got planned."

"It's a surprise."

"Do I have to go?"

"Sherlock."

He sighed and stretched his lanky body to its limit. John opened his newspaper and drank his tea, ignoring any and all glares or pleas. Eventually, the detective fell asleep, all the more distracting because of his snoring.

John sighed and began cleaning up. Molly, Greg, and Mrs. Hudson would be over tomorrow night. Nothing fancy. They'd enjoy dinner (courtesy of Mrs. Hudson), have some wine (thanks to Lestrade), and have cake (prepared by Molly). John knew, of course, that Sherlock would hate it. The detective hated food—which seemed to be what birthdays were centered around nowadays—and despised small talk. No one could ever figure out what to gift him, either. Not that it made much difference. Sherlock usually knew what the present was before it was out of the box. That was the only fun part, John guessed.

But he had a sneaky suspicion that Sherlock never had a birthday party before. Mycroft confirmed it, explaining that birthdays were viewed as "wasteful" during their childhood and spent as any other day. Even if they had been celebrated, John figured Sherlock wouldn't have enjoyed them. But he wanted to give him that. Just one party in his honor.

Sherlock slept from five that night until one the next afternoon. John found him sprawled out in the same position, still snoring and clutching a fist in annoyance.

He placed a blanket over the detective. The party wouldn't start for a few hours. The longer he was unconscious, the better. Sherlock hadn't slept in a few days, either, which was normal but still unhealthy.

John began to walk away but turned around. He felt Sherlock's forehead. Boiling. Palms were sweaty, hair was mopped, and nose was red. Great.

"Sherlock." John shook the detective gently and crouched next to him. Sherlock's eyes opened slowly. "Hey, do you feel okay?"

Before the question was out of John's mouth, Sherlock began coughing. "Alright, come on."

"I'm fine. Get off." Sherlock pushed John away and burrowed into the blanket.

John forced a thermometer into his mouth. 103. "Oh, Sherlock. Come on, now, you've got to get to bed."

Sherlock looked at his watch. "I've been sleeping for…what, ten hours?"

"More like twenty. You've never…hey, hey!" John caught Sherlock as he tried to stand and failed. "Alright, time for bed. Go on; yeah, lean over. There you go…no…wait." The detective couldn't stand well enough with help; John sighed, buckled down his knees, and picked Sherlock up bridal-style.

Sherlock stared in fascination, too shocked to protest. A few steps later, John dropped him on the bed and turned out the lights. "I don't know how you do it, Sherlock. Don't think you're off the hook. We'll have your party next week."

Sherlock groaned and, after a few coughs, vomited on the other side of the bed. John patted him on the back and went to the bathroom for towels.

He came back a few seconds later with a needle. "What's this?"

Sherlock looked up and wiped sweat from his forehead. "What?"

John threw the syringe. "This, Sherlock. I'm a doctor, you know. You got this from St. Bart's?"

"I've never seen that before in my life."

John crossed his arms and leaned against the wall. "You injected yourself with the flu to get out of having a birthday party."

Sherlock cleared his throat and crawled into the covers. "Really, John, you shouldn't treat a patient with just distrust. I thought better of you." John didn't move, though, and Sherlock was too weak to argue. "Well you wouldn't listen. I don't want one."

The doctor left. Sherlock sighed, thinking him gone, and sprawled over the bed. He felt awful (physically; his conscience was clean), but it was worth it. John returned with a small, blue box and handed it over.

"What's this?"

"Your present."

"I don't—"

"Sherlock, take it or I'll smash your skull." John shook his head. "The one on the mantle, just to clarify."

The detective took the box and unwrapped it. A key fell out.

"What's it for?"

"It was Mycroft's key to our flat. He's promised not to stop by for the next month."

Sherlock felt the key's ridges and smiled. "John, I'm…impressed."

"Are you?" John took the key back and placed it in his pocket. "Hmm. Too bad he'll have to come by and make sure you're feeling well."

"What?"

"Well, there were conditions to our agreement, of course. If you're in danger or violently ill, he's allowed to check up on you. As your doctor, I'd say you fit that description."

John patted Sherlock on the head and walked to the door. "If you need anything, just shout."

Sherlock cursed as the door shut.