The first time it happened John thought Sherlock was simply exhausted. He had tagged along with the detective to investigate a body found in an office building. Lestrade briefed them on the situation.

"And she doesn't work in any of the offices here, correct?" Sherlock said, eyeing the woman's body.

Lestrade's head bobbed backwards before he corrected himself. "Yeah. She has no connections with anyone here either. She works in a nursery…"

Sherlock lowered himself onto his stomach beside the woman, seeming to study the tiny splatters of blood on the floor next to her.

Lestrade and John waited. After two minutes, they exchanged a look. It was odd to have Sherlock at a crime scene and not talking. Lestrade stooped down beside him on the floor and asked, "Have you got anything?" John watched as Lestrade leaned over Sherlock suspiciously, then elbowed him in the shoulder. "What are you doing sleeping at my crime scene?" he demanded.

Sherlock sputtered and then gathered himself to standing. He yawned. "Child's parent. Had an affair. Killed her to silence her."

"What?" Lestrade questioned, as it seemed that Sherlock was perfectly content to let that be it.

Looking somewhat irritated, Sherlock turned back to him. "It's so obvious it put me to sleep!" he exclaimed. "What's her name?"

"Kimberly," Lestrade provided.

"Well, Kimberly started having an affair with the father of one of the children she kept. She was going to come clean to the man's wife, and he lured her here to kill her. Simple. Boring. Not worth the energy of getting onto the floor."

Sherlock scowled toward the elevator, a dumbfounded John trailing in his wake.

/

John began to notice the phenomenon occurring at a greater frequency as he spent more time around Sherlock. One afternoon, Sherlock suggested lunch at a Thai restaurant some 15 kilometers away. John agreed, as Sherlock rarely deigned to eat.

On the cab ride over, John happened to glance over at Sherlock to tell him a funny story about one of his patients. Sherlock was slumped against the window, the flesh of his cheek edging up close to his eye. Thinking it to be a kindness, John heaved Sherlock's arm toward himself to prop him up against the back of the seat. Sherlock added to the momentum, however, and ended up sagging against John's shoulder. As it turned out, that was all right with John.

However, at the restaurant not thirty minutes later when John returned to their table from the restroom, he found Sherlock with his head lolled forward toward his spicy soup. Tendrils of curly hair were dangling perilously close to the thick broth.

John flashed a longsuffering grin at a woman who was staring at them, and tapped Sherlock on the shoulder insistently. The detective sniffed airily at being woken up before realizing where he was. He then managed to not look embarrassed as he checked his hair for food particles.

/

It happened again on their first date. John would have been offended if he hadn't been the one to choose the location. A pub was, after all, not the most interesting of places to take Sherlock, but John was nervous and thought that the dark lights and loud music would distract from his awkwardness.

One minute, Sherlock was looking at the crowd contemptuously, then John looked down to sip his drink, and when he looked up, Sherlock was sprawled across three bar stools. John decided to have his beer and enjoy the evening anyway. Sherlock awoke ten minutes later, the imprint of the vinyl seat across the side of his face. He looked sheepishly at John and John smiled back.

"Would you like to go for a walk around the city?" John suggested. "We could talk…might be more enjoyable than this." He vaguely gestured to the bar.

Sherlock nodded and they left.

/

When it happened during sex, it was John's proverbial last straw. John had paid inestimable attention to Sherlock, worshipping his body with his mouth and hands, gently and powerfully. When Sherlock was spent, he insisted that it was John's turn.

John didn't protest. He laid back and got set to enjoy Sherlock's masterful hands as he had many nights before. The pressure as Sherlock gripped him and stroked him was firm and made shivers run up and down John's body. John shut his eyes in pleasure for a few moments. All of a sudden, the movements of Sherlock's hands were becoming more lax and clumsy. John lifted his head to see why Sherlock was slowing down and found Sherlock napping across his stomach.

John had almost left their apartment in a huff. Sherlock managed to stop him, not bothering to dress and he chased John halfway down the stairs.

"Sherlock, for God's sake, put on some pants! What if Mrs. Hudson walks through?"

"John, it's…it's really not you," Sherlock said, knowing that he sounded like a cheesy romantic comedy. "I've had this disorder for several years now…I actually prefer it because it took the place of my insomnia…"

John blinked up at his lover, beginning to understand. "You have…hypersomnia?"

Sherlock nodded. "If my mind is disengaged, I involuntarily fall asleep."

John balked at that. "So you weren't engaged when you were-"

"I wasn't thinking about anything. I got stuck on the repetition of the movement…and of the desire…we can try again…"

John raised an eyebrow. "You know…there are therapies that can help with hypersomnia."

Sherlock rolled his eyes. "Please. I've researched the so-called therapy and tried it out for myself. Null results."

"Slight difference in trying it out by yourself and trying it out with a practitioner."

"Are you proposing that we…"

"I knew you would say that," John said with a playful exasperation. Let's go see if I can't stimulate you long enough for us both to get off…"

/

John began to worry about Sherlock's condition one evening when he got in late. There were signs that Sherlock was home; his coat and shoes were resting in the hallway. John ventured into the bedrooms, but couldn't locate him. He knocked hesitantly on the bathroom door but received no answer. He pushed open the partially opened door and saw two bony knees jutting upright in the bath. His heart hammered against his chest when he saw that Sherlock's face was overrun with water, aside from his nose which was barely jutting out, causing bubbles with everyone exhale.

John pulled Sherlock up frantically by his shoulders, jarring Sherlock out of his mind. "Wha-What the hell?" Sherlock cried.

"You fell asleep in the bath!" John exclaimed. "You might have died!"

Sherlock frowned and sputtered some water out of his nose. "I wasn't sleeping. I was resting."

"Do you even realize when you fall asleep sometimes?" John asked. "I really don't want to come home and find that you've drowned or tipped over a balcony!"

"I was not sleeping, John," Sherlock insisted, moodily. He grasped for a towel on the rack. "Don't be so paranoid."

John searched his partner's face for any tells. As always, there were none. "Just…be careful," was all he managed. He hated the emptiness of the phrase, but without Sherlock confiding in him, he had little choice.

/

By far the most amusing time it happened, John and Sherlock were in a conversation about their families.

"Harry always did her best to get my goat! She loved it when she knew something that I wanted to know. I think she really enjoyed making me beg her to tell me things…did Mycroft have any annoying quirks?"

Sherlock's eyes narrowed. "Do you really have to ask that question? Mycroft has been a thorn in my side since the first memory I have."

"And what memory is that?" John asked, genuinely enchanted at the prospect of Lil Sherlock stories.

"I was toddling about, and for some reason Mycroft…took it upon himself…to try to…" And just like that, Sherlock fell asleep mid-sentence. John pouted. It was just like what Harry had done to him, leaving him aching for the end of a sentence!

/

By far the most dangerous and painful time that it happened was the time that Sherlock "borrowed" a bicycle. He and John were in pursuit of an informant when the man suddenly hopped a bus, leaving them scrambling for a cab. But Sherlock knew the bus's route. Of course he did. So he appropriated an unchained bicycle from a street corner and sped after the bus. John was left alone, calling Lestrade for backup.

Twenty minutes later, John received a text.

Found Harmon. Lestrade apprehended. Fell asleep while riding back to you. Hit a parking meter. Please come find me. My head hurts. SH

John found him a few minutes after racing off in the direction the detective had fled. Sherlock was sitting on the curb beside the bicycle, its front wheel mangled.

"Maybe we should try to get you into a sleep clinic," John said mildly.

Sherlock squinted up at him. "Perhaps…"