John panted for breath as he ran after Sherlock's quickly disappearing figure.
"Hurry John!" Sherlock called back down the empty street, his voice echoing off the dark buildings until John could barely tell where it was coming from.
He forced himself to run a little faster, but it was no use. A few moments later he heard a scream from down an alley father ahead.
"Sherlock! Oh god oh god!" John gasped out as loud as he could manage. He started to sprint for the unlit alley.
"Sherlock, can you hear me?" John jogged down the street, ignoring the dank puddles he was splashing through. He felt his panic rising as his eyes adjusted to the dark and he saw a figure hunched over another shape near a brick wall. John slowly reached for the gun hidden in his jacket. Knowing he no longer had the element of surprise, he walked as quickly as he could to the figure and held the gun inches from its head.
"Turn around slowly and I swear I won't kill you. For the moment at least." John growled.
"I assure you there is no need for that John." Sherlock's baritone voice murmured.
"Sherlock? Jesus Christ, what are you doing?" John fumbled around in his pockets for a torch. He flipped it on and Sherlock shrunk back, pressing against the brick wall.
Ignoring Sherlock, John shone his torch onto the culprit lying on the ground.
"Oh shit-" John muttered, kneeling down.
The man had the most terrified expression on his face that John had ever seen and his neck was torn open, blood spilling out onto the cobblestones, staining his clothes. John swore he saw him twitch once more before his breathing finally stopped.
John stood up slowly, knowing there was nothing he could to do help.
"What. Did. You. Do. Sherlock?" he growled, his fist clenched, his eyes never leaving the body on the ground.
Sherlock looked up at John's face and stepped away from the wall.
"I'm afraid you'll have to elaborate John." he stated, his voice perfectly calm.
In a flash, John grabbed Sherlock's collar and shoved him against the alley wall. Sherlock smirked at him with a look that said 'What took you so long?'
"You know bloody well what I'm talking about! What did you do to this man?" he forced his voice not to shake. "How did you manage to-" he choked, unable to finish.
Sherlock didn't answer; he simply stared at John's face with what he could only describe as rapture. John shivered at the intensity of his pale eyes.
"How..." he dropped his hands, turning back to the body lying in a crimson puddle.
Sherlock was suddenly on the opposite side of him, close but not quite touching.
"I really don't think you want to know."
John jumped a little but managed to stay calm.
"I really think I do." he choked out.
Sherlock pressed his nose to his neck and John hissed in surprise at how cold and wet it was. 'Wait?' John thought. 'Wet? That can't be right, why would his nose be wet?'
"But that's no fun." Sherlock cut into his thoughts and nuzzled closer. "I want you to guess." he whispered.
Sherlock opened his mouth on the side of John's neck, his teeth scraping his skin. John shivered at how sharp his they seemed to feel.
"No..." he murmured.
John could practically hear Sherlock smirk between kisses.
"I want you to think John. Really think. I never eat, or sleep, or hardly stop to rest at all. Think about it." he prompted.
"It's a little hard-" John gasped, "hard to think with you kissing me like this."
Sherlock looked up, grinning madly.
"On the contrary. I am helping your body release adrenaline, thus speeding up your thought process." he returned to John's neck, now nipping playfully.
John groaned quietly, lightly trying to push Sherlock away. Suddenly Sherlock stopped, lifting his head up and shoving John away, but not letting go of his arms quite yet. He sniffed the night air a few times, and then scowled, pulling John back to his side.
"Lestrade and Mycroft will be here soon."
Sure enough, a few moments later a wailing police car screeched to a stop in front of the alley with one of Mycroft's infamous black compact cars quickly following suit.
Lestrade jumped out of the black car and told the driver to turn so that his headlamps were shining down the alley.
John saw Sherlock flinch away at the light, but he still managed to keep his cool, nodding coldly at Lestrade as he jogged over to them.
"William Parks. 35. Photographer. Thief. Murderer." The consulting detective licked his lips slowly. "Type AB positive, if you were wondering."
Lestrade glared at him. "I was not, in fact." he glanced at Parks' body as Mycroft walked up.
"Why did you have to kill him Sherlock?" Mycroft sighed. "Just another huge mess for me to deal with. Or is that exactly why you do it?"
Sherlock shrugged. "I was hungry." he muttered. "And he deserved it."
"Don't be childish." Mycroft chided. "You need to feed more selectively. I can't keep cleaning up your messes every other day."
John groaned and leaning against the wall, feeling faint. "Shit, you know too?"
"Of course I know, Doctor Watson. I am his brother." Mycroft scoffed. "Well, not in the biological sense."
"Alright, let's not overwhelm him." Lestrade cut in. "Sherlock, can we trust you to get John home safe?"
"What are you implying?" Sherlock growled.
"Nothing, just-"
"Yes, you can trust me. Come on John." He grabbed John's arm and dragged him toward the car Lestrade and Mycroft had come in. "Let's go home."
Dazed, John could do nothing but follow behind and before he knew it he was sitting next to Sherlock in the back of a car racing toward their flat.
"Why?" John muttered staring out the window. He heard Sherlock slid over the press up against him.
"Why? Why didn't you tell me?"
Sherlock paused and John felt a pang of surprise. Sherlock hardly ever had to think before he said something. "I don't know."
"Don't lie to me." John growled, turning around to look Sherlock straight in the eye, smirking in satisfaction for just a second when he flinched. "Don't you ever dare lie to me."
Sherlock still didn't answer.
"Fine. Then why did you have to kill him? Will Parks."
"You've been working with me John. You know how many people he's killed, this was the only way."
"Sherlock, he wasn't even armed!"
Sherlock shrunk back into his seat. "I... couldn't help it... I'm sorry, I'm just a monster. I'm sorry." John saw him wipe his eyes on his sleeve. "Fuck, I can't even cry!"
John let his face soften and he put a hand over Sherlock's shoulder, unsure what to do.
"Let's just... Start at the beginning. Tell me everything."
Sherlock took a shaky breath and began his story.