Wind whistled through his ears; arms and legs flailing, pinwheeling, trying to keep him afloat and fighting helplessly against the wind, and then WHAM.
Into the truck full of cushions. Just like that.
John took a deep breath, shaking lightly, adrenaline coursing through his veins. He was slightly dazed and did a quick check to make sure he was alright physically before standing up and attempting to wade through the bags and boxes and cushions and who-knows-what.

Then the truck moved.

John fell awkwardly onto a cushion and yelped in surprise, head shooting up to look at the driver. Then he saw the passenger and the gun. It was just his luck that the truck he landed in would get carjacked with him in it. Better call Sherloc-
Oh. The phone. He tossed it on the roof.

Damn.

Sherlock had caught his breath watching John jump (oh god he jumped he did it as planned the truck what if he misses the truck he can't I made it my legs are longer oh god JOHN) and then broke into a sprint to catch up to him, to apologize, to do who-knows-what but know he was wrong and John was right—

-but John wasn't there. Nowhere, in sight, him or the truck they'd asked to borrow for him to land it. The detective's eyes widened and he spun around, trying to make sense of it.
"John! John!"

And then it hit him; the truck. He had noticed someone walking that way, they must have carjacked the truck. Or kidnapped John. This was distressing.
He looked around, quickly, analyzing, observing, doing anything he could to pick up John's trail; then ran after the truck, quickly, as quick as he could pace himself, trying to figure out how to intercept it best. This wasn't a taxi, he couldn't just jump in front of it.

Well he could, but John would not like that.

So he ran hard, weaving through London, his mind working a route and chanting a mantra of John to keep his breath steady.

John, however, was quite content here for the minute. He didn't hurt too bad, but he was sore, and making a makeshift chair from a few cushions he had settled in, for the moment. All the while he kept glancing out at the street (stoplight, sign, caught in traffic, we're moving slow enough, come on Sherlock). He knew the man would find him; but then he saw Scotland Yard and decided to hell with it, and got out, walking into the building casually to speak with Lestrade on a recent solved case.

Sherlock chased the truck for hours, it seemed, getting it in sight (there it was red truck slats all the cushions and boxes and bags John where was John)—

-and watched as the truck swerved, and crashed into the Thames.

"No…John. John, no…no nononono John, John!"
He ran on impulse, not knowing where he was going or what was happening but John was in trouble, John was in that truck and the truck was in the Thames and oh god.

There was nothing he could do. The thought sunk in his chest, into his stomach and settled. It had all gone awry. Another of his stupid ideas had hurt John, he had hurt John it was his fault and John was at the bottom of the Thames because of him (Stupid Sherlock Stupid you knew this would happen he'd get hurt because of you it was stupid to let him come along and yet he wouldn't have had it any other way past tense why was it past tense).

So Sherlock walked home, his eyes staring blankly ahead and the world falling down around his ears; barely able to drag himself up into his chair before collapsing.

John walked back out of Scotland Yard with a bit of a pleased expression before trying to catch a cab. It took five tries and then he got fed up and just walked. A pleasant stroll couldn't hurt after earlier—hello, what's this? He walked over behind the crowd gathering near the river and managed to sidle his way to eavesdrop in on gossip.
"—truck fell into the Thames—"
"—no one survived—"
"—what an awful thing—"
John's blood ran cold as he heard them. No survivors. No survivors oh god what if Sherlock saw and hadn't seen him? What if he hadn't caught up before this—or what if he was in the truck? He set off at a run, sprinting as fast as he could back to the flat, bursting through the unlocked door like a madman and up the stairs before Mrs. Hudson could even make it out to admonish him.
"Sherlock!"
The man snapped to attention, his eyes widening as John stood panting in the doorway. His eyes were dull and he was a bit paler, like—oh.

"Uh…"
"John…"
John shifted, suddenly somewhat awkward now he burst in here like his life depended on it. Granted, in a way, it had.

The look Sherlock was giving him now (disbelieving but hopeful; oh god so sorry) didn't help.
After a minute under Sherlock's gaze, John cleared his throat, about to speak, but the detective moved, and in a few loping strides pulled John into a tight hug, murmuring an apology over and over.
"A-ah, Sherlock, whoa, wha—you're apologizing? Wha—No, no I should apologize, I suggested the whole thing—"
Sherlock cut in sharply, and now John could feel the subtle tremble underneath that the detective tried to hide.
"No, you were justified in trying to show me, I had not considered the carjacking or the Thames—"
"You saw that—"
"I was there."
"Oh."
Oh. No wonder Sherlock was so distraught. He thought he had watched him crash after surviving the building.
"Okay. List of things never to do again; jump off buildings."
"Agreed."
"Uh, Sherlock?"
"Yes John?"
"You can let go now."
"…Apologies." And the man stepped back, a bit awkward, slightly bashful. Just like when the tables were turned not two months ago. The wound was stinging still, this didn't help. John took a deep breath, and then an idea came to him; so he smiled, and looked at the detective.
"Sherlock."

"Yes John?"
"I'm not dead. Let's have dinner."
Sherlock stared for a second, then they both burst into nervous giggles, soon dissolving into laughter as the tense air dissipated in their companionship.

"Lead the way, John."

"Off we go!"

And so they did.