Sherlock leaned against the cool stone wall of the building as subtly as he could manage, his eyes settling shut slightly longer than normal as he exhaled slowly through his nose.

The sharp sounds of London faded into a blurry murmur of whirring wheels on damp pavement occasionally interrupted by a squawking horn.
The crown of his head had just hit the hard surface when he was yanked unceremoniously from his reverie by a familiar voice.

"We can go home if you want," John muttered concernedly, sidling up to Sherlock.

"Ermph," Sherlock quickly cleared his throat when his voice failed to make words. "I'm fine, besides we shouldn't be here much longer anyway." He puffed out a cloud of steam in the crisp night air.

"How many hours has it been since you've slept?"

"Approximately thirty-six," he said without missing a beat.

"They don't need us here, you know. Even you have to sleep, Sher, they won't think less of you for going home after working the case harder than any of them."

"I refuse to trust these imbeciles with a case so fickle as this, John."

"Well, you're not going to be much help if you can't even stand without falling over." Sherlock turned to his companion, though his icy stare didn't seem to be affecting him in the least.
He settled his head more decisively back against the wall, breathing deeply. After what only seemed like a couple seconds of having his eyes closed, Sherlock felt his arm being jerked sideways in a most unpleasant fashion.

"Urf," he said intelligently.
John smiled in amusement, grabbing his shoulders and hauling Sherlock into a more vertical position. "You were literally falling asleep on your feet." he joked as the taller man blinked his eyes fully open.

"M'fine," Sherlock muttered unconvincingly, trying and failing to remove John's supporting hand without sliding down the wall again.

"Alright, Mr. Holmes we're going back to the flat," John chided, sliding his arm around Sherlock's waist and waving to Lestrade with a thumb flicked in the direction away from the precinct. Sherlock swore he saw him smile at John half-carrying him to a cab. Not that John hadn't fully carried him at least a couple times, but that is definitely a story for another day.

"You don't have to let it get this extreme, you know." Sherlock made a noncommittal noise, sliding his feet with as much energy he could muster in the direction of the street. John sighed. "You're a complete idiot, Sherlock Holmes." The addressed just smiled sleepily at the remark.

"Only when you're around John."