After the fifth attempt to hail a cab, Sherlock was getting frustrated. (It's only pig's blood! The cab drivers know I'm not a criminal, for God's sake!) He'd determined the murder weapon by harpooning a pig, but in order to find a pig with a willing owner and enough space in which to harpoon the pig, he'd had to take a cab to Colindale – thankfully, the cab driver had owed him a favour – and now, he needed to get back to Baker Street. The pig's blood was sticky on his skin and he could feel himself sweating in the unseasonably warm weather. Sherlock's skin was crawling, he was beginning to smell, and it was all he could to not to start screaming.

The sixth cab driver told him in no uncertain terms that he'd never get in anybody's cab looking like that. "Nobody wants blood on the upholstery after that Jeff Hope business," the man had said before speeding off.

Sherlock grumbled curses at the retreating vehicle, and then snarled under his breath as he looked down the road. Baker Street was too far to walk and the next bus wouldn't arrive for thirty minutes so he was left with one option: take the Tube.

To say that Sherlock hated the Tube would be an insult to the things Sherlock actually did hate. Sherlock didn't merely hate the Tube; he wished the Tube would be sucked into the centre of the Earth and dissolved in magma until it melted and all traces of its existence were gone. The crowds, the smells, the heat – all that useless data threatened to fry his hard drive. (Why can't Mycroft's people get rid of the bloody thing, or at least make it more civilised?)

Still scowling, the detective made his way to the platform at Colindale station and consulted his mental Tube map. (Currently on the Northern Line, must connect with Circle, Hammersmith & City, or Metropolitan to return to Baker Street. Which means I must change trains at King's Cross, the only place in London with more moronic tourists than the Baker Street station. If there were a merciful deity in the heavens, it would strike me down and spare me this misery.)

Things started out well enough. Only one other person was waiting for the train, and when Sherlock got on, the other man swiftly proceeded to the opposite end of the carriage. (Cheap suit, likely the only decent one he's got, old shoes, recently polished. On his way to a job interview, hoping the stench of pig won't get on his clothes. If everyone else is of his sort, I might actually have a tolerable ride.)

The detective should have known better than to get his hopes up. At the next stop, four teenage girls skipping school got on the train and began gossiping loudly about their classmates, their plans for the weekend, and giving Sherlock looks of disgust. One of them approached him, clearly on a dare from the others.

"Excuse me," she said with a giggle, "Have you seen the white whale?"

Sherlock gave her a look that would cut titanium and replied, "No. But I can see that you and your fellow imbeciles are destined for a life of menial retail jobs and council flats, one of you already has gray hair and the other three will be gray by age thirty, and one of you is pregnant and will be abandoned by the father."

The girl turned beet red and rushed off, and the four began arguing over which of them was pregnant. They exited the train at the next stop, their cries of "Not me!" and "It's totally you!" echoing through the station. Sherlock gave a smug smile. (Just wait until the redhead finds out that her boyfriend fathered the blonde's child.)

Sherlock passed the next few minutes in relative peace. A few people had filtered onto the train over the last few stops, but the detective still had empty seats on either side of him. And then the train reached Camden Town station, and a great crush of people made their way onto the carriage, cramming all the available seats and most of the standing areas. Sherlock began drumming his fingers on his knee; the data was starting to overwhelm his processor, but perhaps if he focused on one person at a time he could prevent complete system failure. (Man in black trousers: Accountant, adulterer, just had "lunch" with mistress, has two children who resent him. Man in khakis: software engineer, on holiday, married to woman sitting next to him. Woman in blue: gardener, first time in London, revoltingly happy. Man in skinny jeans: musician, plays guitar well but won't listen to people who tell him he can't sing and oh for God's sake, what is that SMELL?)

The odor that interrupted his string of deductions was a person two seats down tucking into curry takeaway. (Mid-forties, recently divorced, Harry Potter fan, never learnt to cook, subsists on takeaway, seldom washes hands.) The detective stewed for a moment. After studying the eating idiot and the musician, a plan formed in the detective's mind and he stifled a smirk.

When the carriage came to a stop at Euston, Sherlock made a small adjustment in the position of his foot, causing the musician (who was sublimely unaware of his surroundings) to trip. As the musician went sprawling forward, his messenger bag swung along with him and collided with the idiot's lunch, knocking lamb vindaloo all over the idiot's shirt. With a startled yelp, the idiot jumped up and began cursing at the musician, who swore it was an accident. The two men continued arguing as they disembarked. Sherlock pretended to ignore the whole scene and everyone else on the train pretended to ignore him.

Changing trains at King's Cross was easier than it had ever been for Sherlock, mainly because everyone was keen to get out of the way of the tall, blood-covered man carrying a harpoon. He smiled quietly to himself as the passersby skittered away from him like frightened mice. (If I didn't care about ruining my clothes or smelling like a butcher shop, I would do this every day. It makes avoiding idiots so much easier.)

The detective stepped on to the platform just as the next Circle line train arrived. (Eleven more minutes to the Baker Street Station, then one minute's walk home.) The train lurched out of the station, started off at a brisk pace… and ninety seconds later, came to a stop.

The conductor's voice came on. "Ladies and gentlemen, we apologise for the delay. This train is being held at a red signal. We expect a delay of three minutes."

Sherlock cursed under his breath. The pig's blood was starting to congeal on his skin, his blood-stained shirt was clinging to him, and the sensations were making him itch all over. He considered scratching, but dismissed the idea as it would result in blood under his fingernails. (Even with diligent handwashing, it would take days for the last of it to wash out. Unacceptable.)

To distract himself, the detective reviewed the names, molecular structure, and uses of all the known allotropes of carbon. (Diamond: atoms covalently bonded in a tetrahedron, which form a network of 6 membered rings. The rings are in the chair conformation, and lack of bond angle strain gives the diamond its hardness. Industrial applications include drill bits, grinding, and polishing…)

By the time Sherlock arrived at carbon nanotubes, the train was moving again. (Finally. Two more stops and I shall be at Baker Street.)

As the doors opened at Euston Square, he surveyed the incoming passengers. (A dozen people with matching hats, many of them wearing bum bags and white sneakers and speaking far too loudly – I can hear their every word from here. American tourists, likely on their way to Madame Tussaud's. Could this day get any more annoying?)

The tourists all gasped as they came aboard, and he gave each of them in turn an evil eye.

Sherlock enjoyed peace and quiet for the remainder of his commute to Baker Street.