Another what if for the climax of TGG. "That little dizzy spell you had a couple of minutes ago wasn't just adrenaline, Doctor Watson." Friendship, but could be pre-slash if you like.

Disclaimer: Still own nothing, make no money.

SHSHSHSHSHSH

Clostridium Botulinum

"I would try to convince you, but everything I could say has already crossed your mind."

"Probably my answer has crossed yours."

The pause that followed was unbearably tense as Sherlock's aim shifted from Moriarty to the bomb that lay between them.

The long, slender white finger tightened infinitesimally on the trigger…

And then Sherlock's head snapped around at the sound of John's collapse. The former soldier hit the tiles with an audible thud as he toppled from his crouch against the wall to land face down on the floor.

"John? John!" In an instant, Moriarty was forgotten, the snipers ignored, as Sherlock dropped to his knees beside his friend, reaching for his shoulder to roll him onto his side. The doctor's features were oddly expressionless; all but his unblinking eyes, staring into Sherlock's with unmistakable terror.

"John! What's wrong? Tell me! What's he done?" Sherlock demanded, feeling panic and fear and deepest blackest guilt rise in his gut like a tide.

"He can't answer, Sherlock," Moriarty all but purred. "That little dizzy spell you had a couple of minutes ago wasn't just adrenaline, Doctor Watson. Light-headedness, dry mouth and throat, all that blinking you did because you could barely keep your eyes open… Facial muscles are always the first to go; then shoulders, arms, legs… and the lungs and diaphragm last. I imagine it's an unpleasant death, imprisoned in a body that ceases to obey you," he added casually.

"Clostridium Botulinum…" Sherlock whispered.

"Well, to be quite accurate, I only had him injected with the toxin produced by the bacteria. I've made a lot of progress in my biological warfare since Carl Powers; but when you suggested this pool, I just couldn't resist," he giggled.

"Getting a bit predictable, aren't you?" The detective sneered. "The same answer, three times in a row?"

"Ah, but that's the beauty of it; repetition's the last thing you'd expect from me."

"Why go to the trouble? You were going to blow him up anyway."

"But this way I get to offer you one last puzzle. One chance to save John Watson's life; which he just offered freely to save you. The one, sole, solitary human life in the world you care for."

Moriarty's already inky eyes darkened, glittering coldly in the shifting light. "Your very first mistake."

"And your very last!" Sherlock yelled, rage suddenly overwhelming him as, in one fluid move, he brought the gun to bear on that sadistic smirk.

"Ah, ah, ah, Sherlock!" Moriarty produced a vial of clear liquid from his Westwood jacket. "Wouldn't want me to drop the antitoxin on this hard floor, would you? I'd estimate he has three minutes left before he stops breathing; maybe four, at the outside."

"What do you want?" The words were clipped, jagged with emotion.

"Right now, the price isn't all that high. All you have to do is get up and walk away."

"And you really expect me to trust you?"

"My dear Sherlock Holmes… what choice do you have?"

The answer hovered in the charged air between them. None, that doesn't involve John's death.

"If I agree?" Sherlock bit out sharply.

"Johnny here gets to stay with me; and you get to go home to your skull. Don't worry, I promise I'll feed him, and walk him, and clean up after him; scout's honour." He made a little mock scout salute with his free hand.

Sherlock's blue-grey eyes flickered from John's slack features to Moriarty's smug ones, knowing the consequences of refusal… and knowing that there was only one possible course of action.

He lowered the gun and bent close to whisper a few words into John's ear. Then the detective straightened his long limbs and rose to his full, imposing height.

"This is not over, Moriarty."

"I know," the criminal replied with a grin. "Thrilling, isn't it? Clock's ticking."

Sherlock allowed himself one final glance at his flatmate, lying prone on the floor, and then pocketed the gun, turned crisply on his heel and walked away.

It was probably the most difficult thing he had ever done in his life.

"Toodle-oo, darling!" The criminal crowed, high pitched and playful once more. "I'll stay in touch… I promise."

The moment Sherlock had stepped through the exterior door into the freezing night air, the deafening explosion behind him knocked him flat on his face.

SHSHSHSHSHSH

Was Sherlock ignoring Moriarty to go to John a bit OOC?

The blinking thing I know a lot of people think is an SOS, but when I looked up the symptoms of botulinum poisoning on Wikipedia it does say that heavy eyelids is one of the first signs. It fitted pretty neatly into this idea, especially with Watson's near collapse after Sherlock takes the vest off him. If the source isn't accurate… well, never mind. I thought it was an interesting scenario.

Any thoughts or suggestions welcome…