***Author's Note***
This story was written for my dear friend notjustmom's upcoming birthday. She had requested a Johnlock story based on a theory I had about John hating riding the tube. That was ages ago, and I only just got around to it. I had originally hand-written the story, but she encouraged me to type it up and post it. So here it is. Johnlock is not my norm, nor my forte, but this story is a birthday gift, and how could I say no to the birthday girl?

John would follow Sherlock right into hell. He would. Without hesitation. Had done, actually. True, it had been a hell of their own making. Too many years of not talking. Too long hiding, lying to themselves.

But after Magnussen, and Culverton Smith, and Eurus. After the dust had literally settled and 221b was 221b again. After John had learned it was okay to grieve - Sherlock too - and that there are some things you can't ever forgive yourself for, you just have to grow and do better. After John had eased back into 221b with Rosie. And after he and Sherlock both realized what it was to need, and to finally let go, John finally understood.

They'd been to hell. He'd hated it. Hated himself. But if Sherlock were to ask him, he'd follow him to the pit again. He wouldn't give it a second thought (a bit not good, considering they had a daughter now). He would. John Watson would follow Sherlock Holmes to hell. To the far reaches of the universe. To the unexplored depths. One word. One look. John would be there.

Even before Sherlock fell, before the pool, before he'd shot the cabbie, John knew. He'd do anything for Sherlock. He might bluster and complain, but there wasn't anything he wouldn't do. And Sherlock knew it.

But this… John's steps faltered, and he drew in a deep shuddering breath. This… It was too much.

He'd never told Sherlock this secret. He'd always just assumed Sherlock had read it in the way he folded the morning paper, or his choice of shampoo. Or, perhaps the more obvious tell: that he avoided this particular method of torture at all costs. Literally.

Clearly he'd overestimated Sherlock's deductive prowess.

"John. Come on." Sherlock didn't even look back. How he could know John had stopped running after him, but not sense the clearly unguarded emotion that had to be radiating off from him and echoing in his breathing, John would never know.

"Sherlock, I-"

"John." Sherlock did slow then. He turned back and grabbed John's sleeve. "We have to catch this train. It's vital to the case." He tugged once, gently, on the sleeve, then slid his hand down to John's bare wrist and inelegantly pulled him toward the tube entrance.

John attempted to plant his feet, to counter Sherlock's momentum with his own mass, but Sherlock caught his eyes with a glint in his gaze and the flash of a boyish grin. John shifted minutely and it was enough for Sherlock to tug once more, less gently, and force John forward.

"But… Sherlock, wait-"

"No, John. Both victims departed from this station, on this train, at this time. We have to recreate the pattern as closely as possible. At 9:15 on a Tuesday morning, most of the passengers on this train are here habitually. With a purpose. Someone had to have seen something! Now. Come. On!"

Sherlock quickened his pace as he flounced down the steps to the tube. John stumbled and had to run to keep up with him, connected at the wrist as they were.

John had a flash of another time they had run, cuffed together, connected, Sherlock leading him blindly into darkness. He blinked hard and shook his head to try to banish the image. Breathe. He had to remember to breathe.

At the bottom of the steps Sherlock paused just long enough to get his bearing. John used the moment to wrench his wrist free from Sherlock's grasp. No way was he letting the mad bastard feel his pulse as he marched him into the one place that embodied all of his waking fears. Well, most of them.

How was it possible a bloody Londoner was afraid to ride the tube? It was as much a part of everyday life as tea, or… Or… Riding the bloody tube.

He felt his face flush with shame, and Sherlock chose that moment to turn to him with a frown for the abrupt loss of contact. Sherlock studied John's face with eyes that seemed suddenly more green than any green John had ever seen. He saw only concern and hurt there. John shook his head and motioned for Sherlock to lead on. With a wordless nod, Sherlock hesitated, his hand half raised to reach for John once more, then quickly turned and plowed his way rapidly through the surge of commuters.

Sighing in relief for the momentary reprieve - John knew his partner well enough to know this was not settled - he jogged after Sherlock. The mass of people coursing around him, bumping and jostling him (sometimes he was the one to bump or jostle), murmuring unintelligible apologies, did more to ground him than even the sight of the billowing Belstaff and raven soft curls ahead of him.

Humanity. People living, breathing, going through their day-to-day. He wasn't in a cave tunnel, leading men to sure death, or taking up the rear in order to clean up the carnage. He wasn't marching to captivity. He was in London. Home. With Sherlock. And Rosie safely and lovingly guarded at Molly's flat. This wasn't war.

Nor was it like the last time, when he'd purposely taken the tube from the home he'd made with Mary to Baker Street in order to say his final goodbye to 221b, only because he knew it would force him to steel his nerves. Anything less, and Mrs. Hudson would have been able to see too much.

They weren't even on an adrenaline fueled chase. This was simply an information seeking trip to the tube line. Simple. As safe as central London could be… Surrounded by masses of unpredictable people and entombed underground. John shuddered, heaved a strained breath, and pushed on, catching up with Sherlock at a bank of turnstiles.

"Come along, John." Sherlock jumped over the offending mechanism. John grumbled, got a running start, and followed. A guard shouted after them, but Sherlock just held up the latest MET ID card he'd lifted, Sally's this time, and ducked into the third carriage. John offered a half-hearted apology over his shoulder and made it through the doors as they slid shut.

He stood still by the doors for a moment as the train groaned and rumbled forward, watching Sherlock stalk up and down the length of the carriage twice. The detective glared and looked foreboding, and the effect was obvious as people shied away from him.

John managed a chuckle as he dropped into an empty seat. He leaned back, closed his eyes, and focused on his breathing. Breathing. Not on the vibrations from the carriage floor travelling up through his feet, rattling his bones, and reminding him of jarring convoy transports surrounded by men - boys really - too much heat and sand.

He squeezed his eyes more tightly shut as even in his mind the sun was shining too brightly in the unwanted memory. The clatter of their gear. The quiet chatter, so unlike the boisterous jesting of other days, because their spotter had seen something. High alert. Being rattled and shaken nearly half to death by the massive armored vehicle.

The carriage lurched to a halt. In his mind, John knew that's what was happening. His body though, caught up in the muscle memory of the flashback, traitorously tensed in preparation for impact. When the carriage doors slid open, there was something… Perhaps the tone of the grinding motors, or maybe it was the high pitched squeal of an older gentleman's ill-tuned hearing aid. Whatever it was, the sound was too familiar, too much like the sound he'd heard before the world exploded around him that very last day he'd been considered useful by his country.

John ducked his head and brought his arms up to shelter his neck. He started to dive to the floor, but before he could a familiar weight pressed close against his side and strong arms wrapped around his middle, restraining him. Trying desperately to hold him to the present.

His instincts were telling him to get free. Get low. Shelter. Shout commands. Get everyone to safety.

In his mind, John knew, he knew it was Sherlock holding him, speaking low into his ear. Urgent. Frantic. Sherlock.The name didn't exactly inspire recollection of safety for John, but it brought to mind home. London. Trust.

"We should go. I need to get you out of here," Sherlock urged as he tried to help John stand.

Body tense and trembling, a stab of pain radiated from John's right hip down his thigh, and his knees gave out under him. He sat down hard, Sherlock following easily, never letting go. John gritted his teeth and bit back a terrified sob. "Can't," he gasped.

"Okay. It's okay, John." Sherlock pulled him closer, so that John's face was pressed to his chest; he rubbed small circles along John's spine with one hand and toyed with the fine hairs at his nape with the other. "Next stop. We'll take the next one. Just hold on. Hold as tightly as you need to, John."

And John did. He clung tightly to Sherlock's lapel, the tremor in his left hand so severe, he could not have released the death grip if he'd wanted to. He tried, with little success, to match his erratic breathing to Sherlock's intentionally steady breaths.

The conductor's garbled voice crackled overhead and the gears groaned as the carriage pitched forward. John wrapped his arms around Sherlock's waist, under his coat, and hoped no one heard him whimper. But he knew they knew. They all knew. He could hear them mumbling softly to each other, watching the crazy man break right in front of them.

The idle chatter in combination with the rough motion of the train and the heated, oppressive air of the carriage assaulted his senses, despite being cocooned against Sherlock's chest. Against his every effort, John found himself once more in a convoy in a marketplace in Helmand Province.

"It's too much," he mumbled against Sherlock's chest, his voice breaking, his tears ruining the posh shirt.

"I know, John. I know," Sherlock soothed, holding him impossibly tighter, his mouth directly against John's ear.

"I… Can't. Sh'lock please… I…" John rasped.

"What, John?" Sherlock pleaded. His breathing remained steady and his fingers still moved gently. "How can I help?"

"I need…" John tried again to match Sherlock's breathing. He could feel himself hyperventilating and growing lightheaded for it. As if he weren't already humiliated, passing out and forcing Sherlock to carry him would be mortifying. But his mind, the memories, he couldn't…

"Out. I can't…" John did sob. He couldn't stop it. "I can't get out." He knew where the memory went, what came next. The suicide bomber. The heat and chaos. The staccato of gunfire. Blood. Too much blood. His men. His team. His family. And then his own. "Fuck." He fought a wave of nausea and shuddered against Sherlock.

"I'm sorry… Oh, John I'm sorry. We can't get out now. The next stop is soon. Shhh… Shhh… John, I'm sorry." Sounding absolutely destroyed, Sherlock rambled on, attempting to calm John even as his own anxiety was building. John shook his head against Sherlock's chest.

"My head…" he managed. "I can't get out of my…" He cried out as the train lurched and jerked, the motion causing a twinge in his shoulder. "I'm losing my mind. Help me." He tried to get closer to Sherlock, needed to burrow deeper.

Sherlock slowly moved the hand on John's spine to press, gently, though with considerable firmness, protectively against John's left shoulder. He moved his other hand up and slid his fingers into John's hair, cradling his head. "Breathe, John…"

"Can't…"

"You must. You're going to-"

"'M a doctor," John ground out. "I know. But…" He tried. He honest to god tried to draw a deep breath, but his lungs rebelled. "Can't," he groaned.

And then he gasped and coughed in shock when Sherlock licked - fucking licked - his ear. "Sher-" John panted, still not breathing.

"Breathe," Sherlock whispered right before gently, so very lightly, biting John on that spot. The one just below his jaw. Another time it might have been arousing. It wasn't. But it was effective. John gasped again, coughed again, and finally got his lungs full of air.

"Stop that," John grumbled. There was no heat behind it.

"Breathe," Sherlock repeated.

"Trying." John gasped again when Sherlock pinched his side hard. The one spot Sherlock had figured out was ticklish. "Bloody… Fucking… Bastard..." John huffed without coughing.

"Breathe," Sherlock whispered again, sliding his hand along John's spine to match the rhythm of his own breathing. He kissed John's forehead and mumbled, "Breathe, John. C'mon," as he started rubbing soothing circles against John's scalp with his other hand. He hummed the piece he had recently been composing.

For a moment the sounds of the train, of the other commuters, of his own ragged breathing and racing heart, overwhelmed him, and John shuddered and tensed. Sherlock simply held him closer and continued breathing and humming. As quickly as it all started, John's mind figured it out. He was not in the hell of his personal nightmare, but in London. In the arms of this mad, brilliant man who loved him. The sudden relief was too much. He collapsed against Sherlock and wept.

"Sorry. I'm sor-"

"Don't," Sherlock breathed against John's ear. "Shhh… Don't." He tilted John's head up and leaned down. "John, please. Look at me?"

John nodded and forced his eyes open. He looked into the stormy, sorrow-filled depths of his love's eyes and had to remind himself to breathe again.

"I should have known. Damn it." Sherlock looked away, but turned his eyes back quickly. "All these years, and I never saw." He inhaled deeply. "It's so clear now. The unease you felt when I dragged you into the tunnels that time. It wasn't the bomb-" John snorted and Sherlock managed a chuckle. "Not just the bomb. But I didn't see, I was too caught up, and I overlooked you. I always overlook. I miss too many-"

"Sherlock, no…" John shook his head. He sat up and rubbed tears from his face.

"John, I continue to fail you."

"My broken weakness is in no way your fault." John shook his head again, and dropped his gaze away. "'M sorry for ruining…"

"No! John, no." Sherlock cupped his face in both hands. "No, John. My ridiculously brave, irrationally courageous John."

Before John could respond, the train ground to a halt. Sherlock dragged him up and nearly carried him forward, shoving and snarling his way to the carriage doors and up the station steps to fresh air.

John had no idea where they were. It didn't matter. He gulped the chilled air and considered dropping to his knees to kiss the damp, filthy, blessedly solid ground beneath his feet. Instead, he shuddered as Sherlock pulled him tight to his side and stuck out his hand for a cab.

"Home?"

"The murderer?" John groaned.

Sherlock hummed. "I made him as soon as we entered the station. He didn't realize his mark even left the train because he was focused on you. You saved a man's life today, John." He offered a smile that was weak at best.

"Not helpful, Sherlock." John let Sherlock guide him into the car. "I suppose next week I could-"

"No. While noble, your self-sacrifice is unnecessary." Sherlock took John's hand and gave the cabbie the address. "He was wearing his work name badge. It's only a matter of narrowing it down now. We caught him, John."

"Good. That's good. I don't actually think I could…"

"I would never ask it of you. Never again," Sherlock kissed their joined fingers and whispered, "I wish you would have told me."

"Sorry," John mumbled, clearly still shaken and only just past distraught.

"John." Sherlock pulled him to his chest again. There were so many things he needed to say. Things to comfort, to reassure, to convince John of his own strength. But… No. He kissed him softly and wrapped him up in a consuming embrace. "My John. I love you. All of you."

John leaned against his love and just breathed.