Usually, after a long, drawn out case, Sherlock finally got to go bed. John went to work.

With the last few pounds in his pocket, John hailed a cab. This last case had he and Sherlock out late every night for the last week. He couldn't remember the last decent night's sleep he'd had. Yesterday, it had seemed that the case had hit a dead end. Sherlock had been quiet for hours, sitting in his chair, feet folded underneath him, quietly muttering to himself. John busied himself making tea and reading the paper. Despite his flatmate's frustration at the case, John was secretly pleased with the quiet afternoon.

As the day grew into night, Sherlock continued to sit in his chair, occasionally sipping the tea John had left him. Anticipating the first full night's sleep in days, John headed up the stairs to bed earlier than usual. His colleagues had been commenting on his appearance as of late, remarking on his haggard state. Tonight, he thought, would be a relaxing end to a surprisingly relaxing afternoon.

He should have known.

No sooner had he sat down on the bed to remove his shoes than the sounds of Sherlock's shouts below filled the flat.

"Oh, that is good. That's brilliant. So stupid, but brilliant! John, what are you doing? Let's go!"

With a sigh, John pushed himself off the bed. "Just one night's sleep, Sherlock." Then, louder so his flatmate would hear him, he yelled down the stairs, "Is that too much to ask?" But he couldn't deny; he was excited. After all, this case had puzzled the best consulting detective in all of England for the better part of an afternoon – he was excited to find out why.

SH - SH - SH - SH - SH

And now here he was, hours later, handing over the last of currency in the bottom of his coat pocket to the tired cabby. They had spent the night tracking down their suspect (it was the butcher, of course) through the streets of London. The cold had seeped into John's bones, agitating his old war injuries. He legs ached from sprinting who knew how many blocks to cut off the butcher's escape route. Sherlock arrived just in time to spell out the case for Lestrade who took the butcher into custody. The detective inspector then insisted on a full debriefing, letting the pair go just in time for John to catch a cab and make it to work on time.

He had a full day ahead of him, but some kind soul had just refilled the coffee pot in the kitchen. John poured himself a cup, then headed to his office to start the day's work.

Three common colds, one tonsillitis, and two broken bones later, John was ready to leave the office. His four cups of coffee had done little more than make him jittery all day and if his shaking hands were any indication, he was crashing fast. His bed called out to him like a siren song and he could hardly wait to pass out onto it.

He said his goodybyes as he was heading out, barely pausing to lock his office door behind him. Out on the street, he raised his hand for a cab, simultaneously reaching into his pocket for his wallet…

Only to find nothing. With something he assumed was similar to Sherlock's momentous epiphanies, he could suddenly picture exactly where his wallet was – on the kitchen table where he had left it when they had returned home earlier yesterday. Bloody hell.

It was too far to walk back to Baker Street, and in his current condition, John wasn't sure he could manage it anyway. He had no other options. He pulled out his mobile.

Sherlock, I don't have my wallet. I need you to send a cab. – JW

A minute later, a reply.

Why did you leave your wallet here? – SH

I didn't leave it, I forgot it! Can you please send a cab now? I'm exhausted. – JW

SH - SH - SH - SH - SH

Back in the flat, Sherlock stared at his mobile. It was unlike John to make such an omission. To be tired enough to not only forget his wallet, but to also admit he sleep deprived was very unlike the military man. Calculating quickly, Sherlock decided it had been at least 36 hours since his companion had last slept.

Sherlock stood, grabbed both his wallet and John's, and took off down the stairs.

SH - SH - SH - SH - SH

Outside of his office, John Watson sat on a cold bench trying to stay awake as the sun drained from the sky. He jolted awake as the streetlamp overhead flickered on. He stood up, bones aching, as he saw a cab pull over in front of him. Before he could open the door, it swung open itself. Peering inside, John saw Sherlock waiting patiently for him.

"What are you doing here? I thought you were just going to send the cab," he asked.

"I fancied a drive," Sherlock replied.

John climbed in and settled gracelessly in the seat next to his friend. "Just home, right? No adventures?"

"No adventures," Sherlock promised.

"Good," John said. "I don't think I could manage a run through the streets after some murderer assassin villain right now."

Sherlock snorted. "No, I don't think so."

John smiled over at Sherlock. "Maybe tomorrow. After some sleep."

SH - SH - SH - SH - SH

As the cab he was riding in pulled up in front of John, Sherlock could see the affect sleep deprivation was having on his companion. He wasn't sure John noticed, but the man's limp returned ever so slightly when he went without sleep too long. Looking at him, Sherlock saw the dark coffee stain on the cuff of his shirt, the hands gone shaky with excess caffeine, and the dark circles under his eyes. He had been right to come collect John instead of just sending a cab. Who knew what trouble the man would have gotten himself into had Sherlock not come.

Even now, John was fighting to stay awake. Under the blinking orange glow of the streetlamps as they made their way home, John's eyelids drooped with fatigue. He would not be awake much longer.

As expected, it was less than five minutes later that, with a final heavy sigh, John's head landed on Sherlock's shoulder. His companion had finally succumbed to his exhaustion.

Sherlock watch John sleep. He was grateful to the man; he had proved invaluable on this last case. Without him, Sherlock is not sure he would have been able to apprehend the murderer. He could not deny John these few moments of sleep here in the dark, warm cab. When they are a block away from home, he will wake him, bring him into the flat, and settle him into bed. But for now, he lets John sleep and does not begrudge him his shoulder.

He thinks that's what a friend would do.

A/N: Hello! Please review; this is my first fic, so any ConCrit would be greatly appreciated!