The fourth time was after John woke up from a nightmare.
The most recent case was probably what had triggered it; the victim was a young Middle Eastern woman who reminded John of the mother he'd failed to save after one of the men in his unit had panicked and shot her, thinking she was hiding a bomb, and not a baby.
The whole week had been stressful, with the threat of Moriarty looming, and the memories John would have preferred to have kept buried. Sherlock was being particularly obnoxious, having decided to go cold turkey on the cigarettes and nicotine patches, running about the flat in a manic frenzy with or without a case to occupy him.
When John shot bolt upright in a cold sweat, he realized with a start that Sherlock was in the room with him.
"You were shouting," he said simply.
"Was I? Sorry about that."
"I wasn't asleep."
Of course he wasn't.
"Perhaps it would help you to sleep if–" Sherlock hesitated. If John didn't know better, he might think that Sherlock was nervous. "I could– hold you. You seem to have reacted positively to it in the past."
What? When? The image of tangled sheets and an empty right side of the bed sprang to mind.
"Never mind. Forget I said anything." Sherlock turned to leave.
"Wait!" The word was out of his mouth before John could think twice.
Sherlock turned back to John, genuinely surprised.
"I wouldn't mind. If you think it'll help with the nightmares. I might punch you, though."
Sherlock smirked. "I can handle it."
"Just don't touch my scar or try to hold me down, and you should be fine."
Something in Sherlock's eyes flashed at the words "hold me down," but it was quickly extinguished.
"Understood." Sherlock quickly stripped down to his pants and slid gingerly into the right side of the bed, on his side, facing John. His gaze was unwavering and intense, and somehow made John's breath catch in his throat.
Sherlock kept absolutely still, and John realized he must be waiting for some sign. John closed his eyes and reached forward, and suddenly he was wrapped in warm arms.
His heart was beating faster than before, and with his eyes shut he was hyper aware of every other sensation – the heat radiating off of Sherlock's skin, the soft in and out of his breathing, the musky smell of tea and chemicals.
This didn't make sense. He'd been in bed with Sherlock before. What was different this time? Why was he reacting so strongly?
"Relax," Sherlock murmured, amusement in his voice.
John opened his eyes in surprise. Sherlock was smiling at him, studying his face. His expression matched the face he often wore at crime scenes; utterly absorbed in his observations.
John flipped onto his other side, facing away from Sherlock. He couldn't handle the suffocating intensity of Sherlock's attention right now. Sherlock scooted closer and spooned John, just as John had done when Sherlock had hypothermia. It shouldn't feel this good. It felt... safe. John let his eyes fall closed and drifted back to sleep.
John had woken up with Sherlock's arms still around him. No nightmares had troubled him. But somehow this was worse. He slipped out of Sherlock's embrace and started to get dressed.
"Are you all right?" Sherlock asked from the bed. John froze.
"I didn't know you were awake."
"You know I don't need as much sleep as you do."
John turned to face the wall and struggled to keep calm. Deep breaths.
"I'm sorry."
John whirled around in shock. Sherlock never apologized.
"I didn't know it would bother you so much. I'll let you get dressed." He slipped out of bed, gathered up his clothing (still in a crumpled heap on the floor, John noted with some surprise), and headed past John to the door.
"It... It's fine, Sherlock. I'm fine."
Sherlock snorted disdainfully, not looking at John. "You're a terrible liar, John."
He closed the door silently behind him and John could hear the soft thumps as Sherlock ran down the stairs back to his own room.
