Author's Note: I was rereading the Harry Potter series, and I thought, why not mix two of my favorite things together? And so this was born. Enjoy and please do review!

John's head was pounding as he struggled to open his eyes. The blackness had yet to yield, his eyelids feeling as heavy as iron weights. He tried to remember why he had been unconscious in the first place-he had vague memories of breakfast that morning, (there had been another head in the fridge, and John had decided breakfast was overrated, anyways) but after that there was nothing.

John tried opening his eyes again-and this time he succeeded, blinking away the black. He was sitting on a hard chair in a small, dark, cold room, with the only light coming from behind a water cooler that held about more or less a gallon of liquid in the corner, which had a stack of plastic cups sitting beside it. If there was a door, he couldn't see it.

He was suddenly aware of the sensation of another living presence in the room, sitting behind him. He hazarded a guess of who it was.

"Sherlock?"

John got some incoherent mumbling in response. It was Sherlock, and it sounded like he was still waking up. John was still too sluggish to get up and walk about, but he had enough strength to turn his chair around, which he did until he was facing Sherlock. The detective looked fine except for a large bump on his forehead-John reached up and found he had one just like it on his own forehead-they must have been knocked unconscious and taken to wherever here was.

Sherlock was now blinking rapidly in the same way John had done, then began looking around the room. His eyes came to rest on John at the end of his inspection. "John."

"Sherlock," John said. "What's going on?"

"Kidnapping, obviously," Sherlock said.

"Moriarty?"

"No. Perhaps he planted the idea in our kidnapper's head, but I don't think Moriarty is directly involved this time..." Sherlock trailed off, studying the water cooler. Sherlock stood a bit shakily, and moved over to the water cooler, looking at it from every angle.

Without warning, a mechanized voice sounded from an unseen intercom.

"I see you're beginning to understand what you must do, Mr. Holmes."

Sherlock laughed drily. "Obvious."

"Be that as it may, you have five minutes to decide which one of you will perform the task," the voice responded. "After which, the one who is chosen has one hour to complete the task. If the other tries to complete the task in the original drinker's stead, then both of you, along with a few friends of yours that I have chosen, will be terminated." The voice paused. "If you succeed, you will have your escape. Choose wisely."

There was a crackling noise, and a female mechanized voice spoke. "Five minutes remaining."

"He wants one of us to drink all the water in the cooler?" John asked incredulously. "A bit ridiculous, isn't it?"

Sherlock's face looked pale in the ghostly light coming from behind the water cooler. "It would be if this was just water."

John got up from his chair, and joined Sherlock at the cooler. "If it's not water, then what is it?"

"I don't know," said Sherlock interestedly. "Though I can imagine the effects of it will be severe."

"Poison?"

"In a sense," Sherlock replied. "I don't think our kidnapper plans to kill us unless we disobey the rules. No, I believe he wants to make us suffer in a different way."

Sherlock took a plastic cup from the stack and seemed to be pondering it. "Seeing as emptying this cooler is our only means of escape, its effects will most likely be debilitating enough to keep us from finishing," he said thoughtfully.

"Four minutes remaining," the female mechanized voice droned.

"I know what you're thinking," John said.

"What am I thinking?" Sherlock asked, sounding amused.

"You think you should be the one to do it," John replied, pointing a finger at him. "You're a bloody idiot if you think I am just going to let you."

"I never thought that you would," Sherlock said in an infuriatingly calm manner.

"You don't even know what this stuff is!" John cried, gesturing to the cooler. "How do you know that whatever this is isn't going to kill you eventually?"

"I don't," Sherlock said.

"There you go then," John said, folding his arms.

"What do you suggest, neither of us drink and get ourselves and others killed?" Sherlock asked coolly, turning the cup in his hand.

"No," John said. "I'm going to do it. Like I said, there is no way that I am going to sit here and watch you die because some psychopath dared you to."

"Three minutes remaining." The intercom crackled again.

Sherlock glanced upwards at the sound of the voice, then turned his attention back to John.

"There's just one problem with that, John," said Sherlock, his voice low, intense. "You forget that I will not allow you; I won't let you be part of another madman's game, not this time, not when I have a choice!" He said, his voice rising with each word.

Stubborn git...but John could be every bit as stubborn as his flatmate.

He reached around Sherlock and took a plastic cup. "You don't have a choice."

"One minute remaining."

"What?" John shouted at the intercom, moving toward the sound. "We have at least two minutes, you skipped-"

"One minute remaining." The voice repeated.

"Sherlock, put down the bloody cup!" John said, hysteria creeping into his voice. "I'm not going to let you-" The timer skipped again.

"20...19...18..."

"We choose Sherlock Holmes," the detective announced suddenly, and the timer cut off instantly.

"No!" John cried, but it was too late.

"Wise choice," the male mechanized voice said. "If you deviate from your choice, your landlady will be the first to die. You have one hour." The intercom crackled and went dead.

John cursed himself for his stupidity. "You idiot," he said, addressing both himself and his friend, "you stupid, selfish idiot..."

Sherlock ignored this. "Enough. It's done, there's nothing you can do about it now."

"What if it kills you?" John asked weakly.

Sherlock brushed this away as if it was just an unimportant detail. "I need you to do something for me."

"Sherlock-"

"I need you to promise me that no matter what, you make sure I finish. No matter what I say, no matter what I do, you have to make sure I don't stop."

"I can't-"

"John, please," Sherlock said, his voice sounding far too close to breaking, "If I can't finish, Mrs. Hudson will die, possibly even Lestrade...I need you." His voice softened, and John silently cursed Sherlock for being so stupidly good about emotions at just the right moments. Sherlock needed John, and that was all the doctor had to hear. If Sherlock had to do this, John bloody well wasn't going to leave Sherlock alone.

"...Okay." John said at last.

"I have your word?"

"You have my word."

"Good." Sherlock relaxed visibly. He put his cup under the spout, and filled it. John watched him numbly, feeling as if he just signed his friend's death sentence.

Sherlock held up the cup as if giving a toast. "Your good health, John."

He raised the cup to his lips and began to drink.

John wanted to tell him to stop, but remembering his promise, he remained silent as Sherlock drained the contents of the cup.

"You okay?" He asked cautiously, as Sherlock lowered the cup.

Sherlock cleared his throat . "Fine." He filled up a second cup and drained that one as quickly as the first. This time he paused, and his face immediately drained of all color. He gave a tiny "John-" before staggering forward. John moved quickly, saving the detective from a hard fall. He steadied him, helping him to stand.

John was alarmed to see that Sherlock's forehead was already beaded with sweat, his breath becoming heavy and labored.

"Are you strong enough to fill this up?" He asked gently, handing the detective another cup.

Sherlock gave a curt nod, and though shakily, filled it up without too much trouble.

He hesitated, and John gave his hand a nudge, to encourage him to keep going. "It's alright," he said softly.

Sherlock grimaced and drank for a third time. When he finished, he gasped and crumpled, and John helped lower him safely to the ground. Sherlock leaned against the wall, and he began mumbling something unintelligible, his face twitching.

"Sherlock?"

"No!" He suddenly screamed, pitching forward. "Stop! I don't want to...I don't want to anymore..." Sherlock covered his face with his hands. "Please don't," he said pitifully.

"We have to keep going," John said, though every part of him was screaming 'stop'. "You can do it."

Sherlock began shaking his head, muttering "no" over and over like a little child being forced to eat their vegetables. John took another cup and filled it up for him, pulling Sherlock's hands away from his face and pushing the cup into his trembling hands.

"Come on, Sherlock," John said, hating himself for what he was doing.

Sherlock swallowed hard, and obediently took the cup and drank.

"No more!" Sherlock begged John when he was done, grasping John's hands in a death grip. "Make it stop...please..." Despite this, John pulled his hands from Sherlock's, and filled up the fifth cup, holding it out to him. "This will make it stop," he lied after Sherlock refused to take it. "I promise."

Sherlock was now shaking from head to toe, face white as a ghost and sweat streaked down his face. John had never seen the detective look so miserable and scared.

"Please," John prodded. "Remember who you're doing this for."

"Mrs. Hudson," Sherlock said weakly. "Lestrade."

"That's right," said John encouragingly.

"You," Sherlock added, and he closed his eyes tightly, grimacing from whatever pain the liquid was causing. After a moment, the detective opened his eyes and took the cup, drinking like a man dying of thirst. When he was done, he violently threw the cup across the room.

"Don't you touch him!" He roared suddenly, looking over John's shoulder, seeing things that weren't there. "It was supposed to be me...it was supposed to be me," he moaned. Then, he did something John never thought Sherlock would do-tears began streaming down his face, and John's breath hitched in his throat.

"It's not real, Sherlock, it's okay, no one's hurt-"

"Don't," Sherlock sobbed. "Please, I don't want to anymore, it hurts, it hurts...don't do this to me!"

"I promise it will stop," John said, filling up the sixth cup. "It will."

The seventh, eighth, ninth, and tenth cups were absolute torture for both John and Sherlock-the detective was writhing in pain, screaming and sobbing, begging for release. There were many times when John just wanted to stop-but he had promised Sherlock, and if Sherlock did not finish, both their lives and the lives of their friends would be in grave danger.

It took a good ten minutes to convince Sherlock to take the eleventh cup. "Come on now, you're nearly there...you're nearly there," John prompted. It was true, a few more cupfuls and the cooler would be empty.

"I am?" Sherlock whimpered, looking up at John with red rimmed, watery eyes. His expression was so hopeful that it nearly broke John's heart.

"Yes," John said earnestly. "Come now..."

Sherlock took the cup, and drank. When he was finished, he cowered, curling up into a ball.

"I'm sorry!" He cried. "I'm sorry, I'm so sorry, I'll never, ever do it again, just make it stop, make it stop, I didn't mean to, I swear-"

"It's alright!" John said desperately. "You didn't do anything, it's okay, you're okay!"

Sherlock seemed to barely register his words, flailing his arms about to shield himself from a nonexistent attacker.

John filled up the twelfth cup, and Sherlock, who had stopped flailing and was now laying limp on the floor, allowed John to help him sit up. John put the cup in Sherlock's hands, and moved a hand underneath the cup, supporting it so Sherlock could drink without spilling.

"Kill me!" Sherlock shouted when he finished.

John kept going, filling up the thirteenth cup, and helping Sherlock to drink, trying to block out his sobbing protests.

"John, please," Sherlock pleaded, gripping onto John's hand, his eyes wild and his breathing frenzied. "Kill me..."

"No," John said, his voice shaking. "No. You can do it, this is the last one." He filled up the final cup, and held it out to his friend, feeling like a monster.

"I can't," Sherlock mumbled, attempting to wipe his face. "I can't."

John just continued to hold out the cup expectantly, though his own hands were now shaking. Eventually, after a great, shuddering breath, Sherlock took the cup with trembling fingers, and carefully drank.

"You're done," John said, breathing a sigh of relief as Sherlock tossed the empty cup to the ground. "You're done, you made it!"

Sherlock seemed unable to speak, but he looked the slightest bit relieved, which was at least some of a comfort.

"Congratulations," said the male mechanized voice over the intercom. "You passed my test, you're free to go."

John could hardly believe it. They had done it!

He had Sherlock put his arm around his neck, and together they stood up slowly. They both looked inside the cooler, seeing a small key now sitting on the bottom of the plastic container. John took the now empty container from the cooler and opened it up, dumping the key into his hand.

"Look, we got it," he said triumphantly, showing the small key to Sherlock.

Sherlock opened his mouth to speak, then abruptly, his entire body went limp. John staggered against the sudden weight, and lowered Sherlock again carefully to the ground, laying him flat on his back.

"Sherlock?"

The detective's eyes were rolling back in his head, and he was again muttering incoherently.

"Sherlock!" John cried, realization dawning on him; the effects of the liquid from the cooler had been too much for Sherlock's body to take, and it was now taking its toll.

Sherlock's breathing became raspy and slow, and he didn't even seem to know John was there.

"Don't you die on me," John said, his voice catching. "Don't. You. Dare!" Sherlock wouldn't die, he couldn't die-

Sherlock's head lolled backwards. "J-J..." He mumbled, his eyes unseeing, empty. He raised a hand, reaching up. John grabbed it, squeezing hard, as if he held on hard and long enough it would be enough to help Sherlock himself hold on.

"Sherlock, don't do this to me, don't-!" John said, and his plea was horribly reminiscent of the ones Sherlock had been making earlier...John should have listened, they could have figured something else out! He was so frustrated he wanted to scream, this couldn't be happening, it should have been him, if he hadn't been so stupid- "Sherlock, please," John said. "You can't go. We need you." He swallowed hard. "I need you." This admission came as somewhat of a surprise, he hadn't even known how true that was until this very moment.

Sherlock looked up at John, eyes finally focusing on him, finally seeing him. He gave John's hand a weak, limp squeeze. "I...I'm sorry," he breathed. "Can't...don't want to...don't want to go..."

"No. No." John pleaded. "You don't have to, please don't...for me-"

And of course the detective didn't listen-his head moved sideways, his eyes becoming vacant and empty again, but they were still locked on John's. He sighed, his hand slipping from John's and thudding to the floor with a sickening thump.

Sherlock gave one last, rattling breath, then went completely still.