It starts with the siren. True, the blinding white light is an assault to his senses, but it is the siren which truly takes him back.

Ten. John begins his mental countdown the way his therapist taught him as he runs for the nearest access pad. Breathe, damn it, just breathe.

Nine. The words "ACCESS DENIED" pop onto the screen in angry, red letters. It's no good, his breathing is shallow and hurried now.

Eight. He frantically rams the card through several more times. Access is still denied. Come on, come on.

Seven. The siren stops, and silence falls. You can stop counting now, Johnny boy, it's over. His racing heartbeat seems to believe otherwise.

Six. The lab is quiet now, and dark. The only sounds are his own ragged breathing and the skittering of the few animals left in their cages. It's almost worse.

Five. The bars of one cage have been pried open. Another small voice begins to whisper, Get out, John, get out, in an ever crescendoing loop. He runs to the second door. ACCESS DENIED.

Four. He flips open the cell phone, even though his fingers don't want to work quite right. Ring. Ring. Come on, Sherlock, pick up. Ring. Ring.

Three. The second the ringing ends, he hears it - the growl that sends an icy chill through his blood and starts his entire body trembling.

Two. He clamps a hand over his mouth to stifle the scream that is threatening to escape. Please, no, God, no. He runs.

One. The cage door slams shut, and John isn't sure which shadows are terrifying him more - the ones passing frighteningly in front of his eyes or the ones returning with a vengeance from beneath the Afghan sand.

Zero. The images don't go away the way his therapist promised they would. "I'm safe,"she told him to tell himself. But I'm not. "There's nothing to be afraid of,"he was supposed to say. But there is. There really, really is.

Ring. Ring. The sound jars on John's nerves, though they're already completely shot. "It's in here," he says. His voice is as quiet and ragged as his breathing. "It's in here with me."

What he doesn't say - what he can't say - is that so are the unblinking, brown eyes of the teenage insurgent boy with the grenade he had been forced to shoot his first week in Afghanistan; a never-ending stream of fire flowing out from the blackened frame of his overturned Jeep; and the barrel of an assault rifle pointed a few inches to the left of his heart.

A pause. "Where are you?" Sherlock's voice is crisp on the other end of the line. His tone is not comforting, yet John takes comfort from it.

"Get me out, Sherlock." How many times had he repeated such words under his breath to a seemingly uncaring higher power? Oh, quite similar all around then. "You've got to get me out."

He mumbles something about where he is, and suddenly all the shadows are moving closer. He feels himself being pulled deeper and deeper into the darkness, but Sherlock's voice summons him back. "John? John?" His business-like tone is cracked now, and John can hear concern seeping through.

"Now, Sherlock," he pleads quietly, unsure how much more of this his mind can take. "Please." Please put that mutant brain of yours into overdrive. Please come find me. Please, God, let me live.

Sherlock seems to sense the request implicit in his plea. "It's all right; I'll find you," he says, "keep talking."

"I can't, it'll hear me." If it hasn't already.

"Keep talking," Sherlock insists. "What are you seeing, John? What can you see?"

The face of a boy I killed. The face of the man who nearly killed me. Is that what you want to hear, Sherlock? "I don't know, I don't know," John lies, desperate to shift Sherlock's focus, "but I can hear it. Did you hear that?"

"Stay calm," Sherlock insists. Way too bloody late for that. "Can you see it?"

"No, I..." And suddenly, one terrifying second later, he can, as the phantoms of the past are overshadowed by the one haunting his present. It passes in front of the cage, casting a huge shadow over him. Even through the tarp, he can see its murderous red eyes, its glowing fur...

But when the tarp is rolled back and the lights come back on, it's not a monster that he sees, but Sherlock, hand on his shoulder, calling his name.

"Jesus Christ," he shouts, the adrenaline still humming through his veins. Get out, run, get out while you can. He pushes past Sherlock, out of the cage, into the lab.

"It was the hound, Sherlock," he exclaims. His legs feel wobbly, like they'll give out at any moment, so he paces, back and forth and back again. "It was here. I swear it, Sherlock. It must..."

He's rambling now. He knows he's rambling, but he's terrified if he stops talking for even a second, the scream that's been welling up inside him for the past twenty minutes will take the opportunity to escape.

"Did...did...did you see it? You must have!" A quick glance around the room reveals no hound, and no ghosts, but that doesn't even slow the deluge of visions bombarding him still.

"It's all right," Sherlock says calmly, eyes following John's frantic progress across the room, "It's okay now."

For the first time that night, John says - or rather, screams - exactly what is on his mind. "No, it's not! It's not okay. I saw it!" He stops just short of telling Sherlock exactly what else he saw. "I was wrong."

"Well, let's not jump to conclusions," Sherlock says with that infuriating smile of his, the one that practically shouts, I know something you don't know.

John remembers asking, "What?" but after that, everything kind of blurs together. Sherlock deduces something clever about drugs and rabbits and cell phones, not mobiles.

Then there's a frantic call about Henry, they're off and running again, and it's all moving quickly enough that John almost doesn't notice the shaking that won't leave his hands or the terrifying images lurking at the edges of his vision.

It is only when he's back in his own room at the inn, away from the distraction of the chase and the reassurance of Sherlock's presence, that the fear really starts closing in on him. The room, which had seemed small upon check-in, feels positively minuscule now, and he knows from previous experience that the second he closes his eyes, the second he lets his guard down, all the memories will come crashing in.

So despite being more exhausted than he can remember in recent memory, John doesn't sleep. He asks the barkeep for a strong pot of coffee, earning him a strange look for his trouble, and spends the night blogging - about the case, visiting Dartmoor, anything to keep himself awake.

By the time morning rolls around, John is bleary-eyed and bone-tired, but unplagued by night terrors, so he's calling it a win. So when Sherlock actually brings him a cup of coffee entirely of his own volition, John begins to think the day might not actually be so bad. That is, until he really thinks about the sugar. That's when the whole horrible truth hits him in a flash.

"Oh God," he says, hoping in some insane, optimistic part of his brain that it's not true - that even Sherlock isn't capable of being that callous, that cruel. He knows even as the thought first occurs to him that it's a lie. "You locked me in that bloody lab."

"I had to," Sherlock says defensively, not having the decency to look even a little bit ashamed, "It was an experiment."

"An experiment?" Is that all I am to you? John wants to shout. Just another one of your bloody experiments?

"Ssh," Sherlock says, glancing vaguely at the other people around them.

"I was terrified, Sherlock! I was scared to death." John isn't sure why he's trying to explain - if Sherlock cared about that, cared about him, he wouldn't have put him through the ordeal in the first place.

Sherlock explains it all in his normally superior manner - the usual rubbish about average minds and leaky pipes and sugar. John barely listens. He can't believe he was such an idiot to believe that he was different from the rest - that Sherlock actually understood what the hell it meant to be his friend. That one day, he might even understand...no, definitely no point in thinking about that now.

John remains silent for the whole ride home, though he can feel Sherlock's eyes boring a hole in the side of his head. He purposefully trains his gaze trained on the bleak, Dartmoor countryside passing by outside and keeps it there until they roll up to the curb beside 221b.

He does not wait for Sherlock to park the car properly nor does he respond or even slow down when his flatmate calls after him impatiently. After being drugged, terrified, manipulated, and utterly sleep-deprived, all he wants is the comfort of his own room and his own bed. John knows the nightmares will come, probably worse than before, but right now he's feeling too beat down to care.