Then the watchman called out, "Day after day I have stood on the watchtower, my Lord. Night after night I have remained at my post." - Isaiah 21:8

John always thought himself a patient man. But even he had limits. And three days after the Baskerville case, he finally reached one with his flatmate.

The Baskerville case had been a disaster. It was solved, there was that, but it had left everyone a bit worse for the wear. John's nightmares from Afghanistan had faded away once he could focus his adrenaline on (in Sherlock's words) The Work. Then he'd spent a few days of running after (and away from) a hound, fighting with Sherlock, and seeing a man get blown up. Two of those were side effects from being drugged; one had actually occurred as stated. All were likely reasons why he awoke with a gasp, heart pounding, back in his own bed.

Or it could have been the gunshot he knew he heard downstairs.

John sprang up from his bed, noted his gun was missing, grabbed the first weapon of defense he could find, and raced downstairs. He was prepared to find anything: Sherlock fighting off a gang, terrorists, or possibly his brother. What he wasn't prepared to find was Sherlock standing in his pajamas and dressing gown, calmly firing John's own gun at the wall above the sofa.

"What the hell, Sherlock?" John yelled from his place in the doorway. "I thought you were in danger!"

Sherlock turned his head slightly in John's direction, and raised one eyebrow. "So you came to my defense wielding an umbrella?"

John looked down at the object clutched in his hands. "Well, I would've brought my gun, but…" he gestured uselessly towards Sherlock.

The detective turned back to the wall and fired another round. At this, John threw down the umbrella and strode over in anger.

"Would—you—knock—it—off!" he hissed. "We'll be lucky if Mrs. Hudson doesn't call the police."

Sherlock scoffed and tossed the gun in John's direction, missed John's expert catch and furious glare, and walked towards the wall.

"Mrs. Hudson is at her sister's," he said. Then, more to himself, a muttered "Sight might be a bit off."

"Or maybe you just missed," John replied as he dismantled the gun.

"Unlikely." Sherlock flopped back on the couch and picked up John's open laptop from the floor, shifting his attention to something quieter.

John walked to the kitchen, set on making some tea to decrease his heart rate. "Oh, by the way," he called from across the room, "did you get a chance to read over the Baskerville write-up?"

In reply, noncommittal grunt.

John rolled his eyes. "I printed it off and put it on your bed, Sherlock. How could you miss it?" While the water boiled, he went into the next bedroom and found the printed pages right where he left them: on Sherlock's pillow.

John huffed out a breath in disappointment and grabbed the papers. He marched back into the sitting room and held them out to his friend.

"I wrote this up while you were kipping on the train ride back from Dartmoor. I printed it off and left it on your bed the same evening. How have you avoided it for three days?"

Sherlock raised his eyes from the laptop. "I've been busy," he answered dryly.

John dropped the papers on top of the laptop. "Well, find time to read it. I need to get it published, and seeing as how I was drugged for some of it, I need your help this time. We get this out there, we might get more cases." A pause. "Maybe fewer with hounds."

He had made it back to the kitchen and was waiting on his tea to seep before it hit him. Oh. Mug in hand, he walked back into the sitting room and watched his flatmate.

Sherlock sensed the stare but didn't look up. "I can hear you thinking from here," he muttered. "Though what can be rattling around inside your brain is be—"

"You haven't been in your room in three days," John interrupted.

Sherlock looked back up from the laptop, but didn't reply.

"I put the write-up where I thought you'd see it within twelve hours," John went on. "Twenty-four max. And if you saw it, you'd've read it. And if you read it, you'd've made all sorts of corrections and comments about what I got wrong. But those pages haven't been touched till now."

Sherlock raised his eyebrows, silently asking And so?

"And so you haven't read it, which means you haven't seen it, which means you haven't been in your room, or at least not on the bed." A pause. "And that means you haven't slept in three days."

For a moment, Sherlock didn't react. Then he blinked and returned his attention to the laptop.

"Congratulations, Doctor Watson," he said tonelessly. "With those deductive skills, you can soon replace Graham at the Met."

"Greg," John corrected. "So you're not saying I'm wrong, then? That you haven't been sleeping?"

"Who's to say I don't sleep on the sofa?"

"You don't sleep on the sofa," John argued. "You'll kip an hour on it, or in your chair, but not a proper sleep."

Sherlock looked back at John now with narrowed eyes. "And why are you so interested in my sleeping habits?"

John shoved Sherlock's legs off the sofa and sat down. "Because you said it yourself. I'm Doctor Watson. These are things we medical types tend to notice." A moment of silence went by. "So? Why the lack of sleep?"

Sherlock was looking back at the laptop screen, but his eyes weren't moving. Even John could tell that whatever was on there, he wasn't really seeing it.

The flat was silent for five minutes. John sipped at his tea and stared straight ahead, towards the mantle on the opposite wall. He wondered about the skull, what it knew, sitting there all this time. He wondered if there was some way to ask it instead of the living, breathing man sitting right next to—

"Can't."

It was so quiet John almost missed it, even in the silence. He turned his attention back towards Sherlock.

"Can't? You can't sleep?" John repeated.

No response.

"To be clear. 'Can't,' or 'won't'?"

Sherlock smirked but still didn't take his gaze from the screen. "There's a difference?"

"Medically, yeah. 'Can't' is an ability. Or lack thereof. 'Won't' is a choice."

A pause, but not as long as before. "Bit of both, then."

John took another drink from his mug, considering why he was awake in the first place. He should have known even Sherlock could suffer the same aftereffects of the week they had.

"Look, they won't kill you, but if it's nightmares, then—"

Sherlock spun his head around at this, his face a mix of confusion and amusement. "I don't have nightmares," he argued lightly.

John sighed. "Sherlock, it's fine. It happens to everyone. I'm actually awake tonight because I had one." And because you were doing target practice on our wall, he didn't add.

"Oh, I know," replied Sherlock matter-of-factly. "I saw you in the throes of it when I went up to retrieve your gun."

John squeezed his eyes shut and pinched the bridge of his nose.

"I suppose that's why you didn't wake when I came in. Was it the war? Or the hound?"

John hummed in his throat a little, in irritation and embarrassment.

"Sherlock, you don't just…walk in…a man's room…" John sighed again and shook his head. "Never mind. So if it's not nightmares, then why are you aren't you sleeping?"

Sherlock looked back at the screen and shrugged. "Someone has to stay awake."

Immediately, John became suspicious. "Why? What's changed that we need you to stay awake all night?"

Sherlock shook his head quickly. "It doesn't matter. And I'm telling the truth: I've slept out here some. Just…not in my room."

"Why not your room?"

Sherlock looked up and towards the corner hallway where his room was tucked away.

"It's…too far away. If something happens, I can't hear it. Not in time."

"What would happen, Sherlock?" John knew he was pressing with all the questions, and at any moment Sherlock could shut him out, retreat, and it'd all be over. But they were close to something, and John felt he couldn't be kept in the dark any longer. Not after what they'd been through lately.

"What would happen?" he repeated, softer this time.

John followed Sherlock's eyes as they looked towards his bedroom, then the main doorway, then the stairs to John's room. Then he swung his gaze back round to meet John. John immediately recognized the look in the younger man's eyes. He had seen it that night at the inn in Dartmoor, but he had seen it first at the pool. When Sherlock first saw John at the pool, when Moriarty made him say the words that sounded like he himself was the speaker. Like he had been the speaker on the other end all along.

And Sherlock had looked devastated. And afraid for the first time ever.

Oh.

"Moriarty." John's voice. A statement, not a question.

Sherlock broke their gaze to look back towards the door. "Said he'd see us again," he murmured, running his hand against the back of his head in a nervous tic. "I doubt very much he was lying."

"So you're waiting for him, then?"

Quick nod. Barely perceptible.

"But why now? What's happened that made you think he's coming back now?"

And then John could see it: too many questions. Something was there, beneath the surface, but the walls were back up. John leaned in closer and shifted focus. "You can't start staying up all night, mate. Not for nights on end. You're killing your body, and what good would you be dead?"

Sherlock jerked around, the momentary fear transforming to anger. "And what choice do I have now?" he hissed, nearly baring his teeth. "Last time, I let my guard down." A pause, then a final word: "And."

John knew all the other words summed up in that single conjunction. And you were kidnapped. And a bomb was strapped to you. And I was tricked into believing you were my enemy. And you nearly died. And then we both nearly died.

Holding Sherlock's gaze, John breathed slowly through his nose. "Then we need to work together," he said finally. "Starting with your plan. If you think someone needs to be awake at all times, then we do it as a team."

And with that, John watched as almost instantly, the lack of sleep settled into Sherlock's features. Adrenaline from fear and anger dissipated and the detective's body noticeably slumped in exhaustion.

John reached over Sherlock's lap and pulled away the laptop. He noticed various pages open, no doubt Sherlock's efforts trying to track Moriarty (though he also noticed an inexplicable order for squash balls, so he could never be sure).

Laptop successfully out of the way, John stood and pulled at his flatmate's arm. "C'mon, up you get," he ordered gently.

Sherlock stood, swaying faintly on his feet. John wrapped his arm around Sherlock's waist and draped the taller man's arm across his own shoulder. "What're we doing?" Sherlock asked, aware his speech was starting to slur a bit.

"You're going to bed," John answered as he guided the taller man towards the hallway. "And I'm going to stay awake, right here, and keep watch."

"And if Moriarty comes while I am sleeping, what could you possibly do?" Sherlock murmured, though his eyes were already beginning to close while his head drooped against John's.

Smiling tightly, John decided not to mention his extensive military training, or the times Sherlock himself had seen John's abilities…including when John bested Sherlock in a fight. "Oh, I would wake you up," he said in mock seriousness, and Sherlock hummed in approval.

They made it into Sherlock's bedroom, and John unceremoniously deposited his friend onto his bed. Sherlock reached for the other half of the duvet to cover up, burrowing down until only the top of his head was visible. John patted the younger man's shoulder before leaving. "You're relieved, soldier," he said softly.

On his way out, John considered shutting the bedroom door. But he reckoned that any noise he made puttering around the flat would likely be soothing, reminding Sherlock someone else was on guard tonight.

John made a second cup of tea, fully prepared to spend the rest of the night watching mindless telly until sunrise or Sherlock awoke, whichever came first. Instead, he found himself at the window, peering down to the quiet, almost empty street below.

He was willing to stand there all night, he thought. He would stand between the world outside and the safety of his home, between a dangerous criminal and his best friend. He could be the night-guard, the watchman.

I stand continually upon the watchtower, he thought with a smile.

He did not yet know, he realized, what he was watching for.

John took a sip of his tea and squared his shoulders.

No matter. He knew what he had to protect.

Author's note: thank you for reading! Feedback is always appreciated.