"Are you sure he'll be all right, John?" Mycroft's voice held concern for his little brother.

John Watson shrugged. "I think so. I'll be more certain when you get that sample tested." He pointed to the tightly sealed jam jar that Mycroft Holmes held.

Mycroft's upper lip curled as he looked at the jar. "Why on earth couldn't you just get a blood sample?"

"Have you ever tried to get a syringe into the arm of a 6 foot tall 5 year old? He screamed like I was trying to murder him. It was hard enough to get a urine sample." John winced.

Mycroft raised his eyebrows enquiringly. John sighed. "He didn't even want to co-operate with that. Treated it like a game."

"A game?"

"Mycroft, he put the jam jar on the edge of the bath and attempted to pee into it from across the room! THEN he dared me to do the same. A pissing contest with Sherlock Holmes is NOT my idea of fun."

Mycroft's lips twitched. John gave him a hard look. "Just get the damn sample to your people so we can find out what those bastards drugged him with." John ran a weary hand through his hair. "I'm pretty sure it will pass through his system in the normal manner, but if it should happen to be permanent…" Both John and Mycroft shuddered at the thought.

A quick text from Mycroft bought his assistant up the stairs and she departed with all speed with the jar of urine clasped in one hand, and her blackberry firmly grasped in the other. Mycroft showed no inclination to depart 221B. Despite Sherlock's protestations, his older brother actually did care about him. He glanced around the living room. His eyes fell on a book resting on the arm of his brother's chair.

Mycroft walked across and picked it up. He turned to John with his eyebrows raised. "Moby Dick?"

John gave a short bark of laughter. "The DeHavilland case. The killer was obsessed with the book. Sherlock's been reading it to 'give him an insight into the killer's mind.' Personally, I think he just enjoys the adventure of the story, but doesn't want to admit it."

"Hmmmm. An insane man versus a monolithic creature. One can see the attraction of the tale."

An ominous crash from Sherlock's bedroom caused both men to swing around in alarm.

Sherlock appeared in the doorway, clad in black silk boxer shorts and clutching a harpoon.

Mycroft wondered fleetingly where the hell Sherlock had managed to obtain the weapon. Harpoons weren't exactly common in the Greater London area. His question must have shown on his face, because beside him John sighed, "Sherlock got it on ebay. He keeps it as a weapon against intruders, and occasionally, for sticking pigs."

Mycroft opened his mouth.

"Don't ask. Just don't ask!"

Mycroft shut his mouth with a distinct click of teeth.

Sherlock spotted his brother. "Ah ha! At last. I have the beast cornered! The Great White Whale is finally mine!"

Sherlock began to stalk down the hallway, his eyes fixed on Mycroft.

"Umm, Mycroft?"

"Yes, John?"

"I suggest you run. Now!"

Mycroft needed no further urging. With a speed to rival his brother's fleetness of foot, Mycroft fled through the doorway and down the stairs.

Behind him he could hear his brother in pursuit.

Mycroft crashed through the front door of 221 Baker Street and stopped, momentarily flummoxed. The car was gone. Of course! His assistant had taken it to get the sample to the laboratory. He really only had one option.

Mycroft began to run down Baker Street, zig zagging to make a less easy target for his brother.

Sherlock sprinted through the door of 221 and looked around. He grinned ferally as he spotted his prey.

John was racing down the stairs behind him, his mobile phone clutched to his ear. "Lestrade! I need you in Baker Street now. Yeah. You could say he's having an adverse reaction to the drug. He's chasing Mycroft down Baker Street waving a harpoon. And did I mention he's only wearing his underwear? Lestrade! It's not bloody funny."

John paused, drawing a deep breath. He watched his flat mate and friend chasing an increasingly panicked Mycroft up and down Baker Street.

"Okay. You have a point. It is kind of funny. What? No I won't take fucking pictures!"

Mycroft ran frantically back and forth across the street. He was beginning to feel, somewhat alarmingly, like a mouse being played with by a cat. Fear was not a natural feeling for Mycroft. He fought back a desire to whimper.

For some reason, Sherlock seemed reluctant to actually throw the harpoon. He was clutching it like a spear. Mycroft wondered briefly if it was because he only had the one.

Thoughts wandering, Mycroft zigged when he should have zagged, and suddenly found his brother in front of him.

Letting out a faint despairing squeak, Mycroft spun on his heel, losing his balance and falling heavily in front of the café.

Rolling on his back, he saw Sherlock towering over him, his grin evil, the harpoon aimed squarely at his heart.

Mycroft's heart raced. Sweat broke out on his forehead.

John's voice was soft at Sherlock's shoulder. "Sherlock, think about this…"

Sherlock's grin got wider. "Oh really, John, you don't honestly think I'd stab my brother through the heart? Assuming that he actually has one."

Mycroft looked up at his brother. Realisation dawned. "The drug has worn off."

Sherlock chuckled. A dark, rippling, waterfall of a laugh. "Drug wore off about 15 minutes ago, but it was such fun watching you run around like a mouse in a maze. Besides, the exercise is good for you. Can't have you getting fat, Mycroft. What would Mummy say?"

"You little…."

John grinned as he leaned forward to help Mycroft to his feet. "I'd be careful, if I were you Mycroft. Probably not smart to be rude to a man with a harpoon."

Mycroft dusted his suit off and gave his brother a Look. Sherlock grinned back impishly, shouldered his harpoon, and marched briskly back to the flat.

Mycroft looked around. Baker Street was remarkably bare of witnesses. He glanced up thoughtfully at the cameras. The CCTV footage would need to be destroyed. He really couldn't afford to have any evidence of this little escapade getting out.

Tilting his head, he gave John Watson an appraising look. John chuckled. "Forget it. There isn't enough money in the world to make me forget this afternoon. It was very entertaining."

Mycroft's expression turned sour.

John's smile was wicked. "Look at it this way Mycroft, it could have been a lot worse."

"Could it?"

"Sherlock could have been reading Fifty Shades of Grey." Chuckling to himself, John Watson headed home, leaving Mycroft to ponder, with wide frightened eyes, what could have been.

Author's Note: This story has its genesis in a dream I had where Sherlock was chasing Mycroft around 221B with a harpoon insisting Mycroft was Moby Dick in disguise. I would like to thank my subconscious for providing me with such entertaining dreams that can be turned into plot bunnies.