"John. John!" Eleven-year-old John Watson turned to see a short, pudgy boy hurrying across platform nine and three-quarters toward him. "You're here too!"

"Hullo, Mike," John said, pleased to find a familiar face. No one who knew him and Mike in primary school would call them best friends, but anyone he recognised in this strange place was welcome. The boys shifted their luggage around in their arms to shake hands, then mounted the steps of the Hogwarts Express together.

"Surprised when you got your letter?" Mike asked. "I was."

"More surprised the owl found us halfway round the world," John said with a laugh.

"That's right! How was your trip?"

John's face fell. "It would have been better if Father hadn't been working the whole time," he muttered.

"Ah, well," Mike said. "Where should we sit?"

"Let's find an empty compartment. I doubt anyone would want to sit with me," John sighed.

Mike gave him an odd glance. "D'you know," he said, "you're the second person who's said that to me today." He paused, thinking. "Come along. You might like him." He headed for the back of the train, John trailing after.

"Hullo, Sherlock? Do you mind if John and I sit with you?"

The compartment was empty excepting a tall, pale boy with curly black hair. He was engrossed in a book so heavy John wondered how he was holding it up, and didn't react until Mike repeated the question.

"What? Oh, fine." He watched John hoist his trunk into the rack overhead, then said conversationally, "Hot in the Middle East this summer, was it?"

"I spent most of my time in hotels, so…" John stopped and stared hard at Sherlock, who had returned to his book. "How?" He didn't bother finishing his sentence. Somehow he got the idea the other boy's mind had long since gone on to another thought.

The first half hour or so of the journey passed with no conversation. Mike and John tried to talk, but Sherlock's overbearing silence filled the compartment and stifled any outside noise except the rain drilling against the compartment window.

"Does anyone have the time?" Sherlock said.

"I don't have a watch," Mike said glumly.

"Just a minute." John tugged his trunk from the rack, then collapsed into his seat as the train lurched around a corner. "Eleven thirty-five," he said, once he had dug his watch out of the bottom of the trunk.

"Thank you," Sherlock said. "Muggle-borns, both of you, I suppose?" he asked.

"Yes, both of us," said John. Rubbed the wrong way by the other boy's self-satisfied face as he settled back in his seat, he added, "Is that a problem?"

"Not at all," Sherlock replied. "You'll find no one you'd want to be friends with cares about blood. My whole family is pureblood, but I-"

"-might as well be a Squib, and would prefer it that way, right?" A corpulent boy who had already changed into black robes and a green-and-silver tie swaggered into the compartment, taking up half the space. Sherlock instantly slouched behind his book and adopted a sullen expression.

"What's a Squib?" John asked curiously.

"A Squib," the older boy explained, "is a person of magical parentage with no innate magical abilities of their own."

"Oh."

"Sherlock." When he didn't respond, but gripped his book tighter, the newcomer continued without waiting for a sign of recognition. "Mummy told me to check on you, see you're making...suitable friends." He looked disdainfully at the other two in the compartment. "She said you'd sit by yourself all day otherwise and never speak to anyone."

"You can tell Mummy," Sherlock said, finally sitting straight, "I will be fine. And if you need something more specific in your report, this is Mike Stamford and John Watson. They're Muggle-borns, previous friends. John has just been along with his parents to the Middle East for a business trip. He has an older brother named Harry, and he's planning on being a soldier when he grows up. Enough to be going on with, don't you think, Mycroft?" And without another word, he refocused on his book, ignoring the looks of shock on John's face and the annoyance on the older boy's.

"Well," Mycroft said, "I suppose that will be 'enough to be going on with.' Lovely to meet you Stamford, Watson. Good luck with your new...acquaintance." He turned on his heel and left the compartment.

"We got rid of him easily this time," Sherlock said from behind his book. "He'll be back, never fear. Useless, brothers are," he added in an undertone.

John was inclined to agree with the last sentence, but he had more pressing worries than the reappearance of the enigmatic Mycroft. "How did you know about me?" he asked. "Did Mike tell you?"

"Not a word," Mike said.

"Did you use magic?" he asked, more excited. To his surprise, Sherlock scowled. "Sorry...I guess. But then how?"

"I figured it out." Sherlock looked insufferably proud of the fact.

"Come off it, you did not!"

"I did so."

"Prove it."

"Willingly," Sherlock said, closing his book for the first time since they'd met. "Look at you. Muggle trunks, Muggle watch, Muggle look of awe at everything around you. You couldn't be anything but Muggle-borns. Easy."

"Fair," John said. "Everything else?"

"You answered for both of you when I asked if you were Muggle-borns. How could you know that from twenty minutes' acquaintance? Could have asked him, but you were offended when I asked you, so not likely. Conclusion: you knew each other before this. Don't know how long, but there you are."

"Brilliant!" Mike said, his eyes wide.

John wasn't quite as impressed. "And what about me? You know I've been to the Middle East, you know about my family - how the devil did you know I want to be a soldier? I haven't told anyone!"

"First, I saw your trunk. There were at least five tags on the handle, the ones they put on your luggage at the airport. Most of them were torn off, but two were from Jerusalem and Tehran. You've been in the Middle East. But why? You're very tan, but your wrists and neck are white still. You haven't been sunbathing, besides, you said you spent all your time in hotels. It wasn't a pleasure trip, at least not for your pleasure. It couldn't have been a wedding or family event; five different places? It must have been a business trip.

Now your brother. Your trunk was quite expensive - about five years ago. The name on the front says Harry Watson. So it wasn't originally yours. It wouldn't have been a gift; who gives someone a banged-up five-year-old trunk with their name on? It must have been handed down to you. But from whom? The name is written in a child's handwriting, so it can't have been a parent's. It's blue, which is a stereotypically masculine colour, especially for children. That rules out a sister named Harriet or some such nonsense. Must have been an older brother, then. See?

As to being a soldier, in your trunk are two pamphlets about the British army, one about the Israeli army, and an adult's book about the history of the Second World War. You're eleven and already picking up pamphlets? Also, you have a military haircut and you try to stand like a soldier. Already practising. This isn't just some whim; this is a calculated plan. There now."

"That was amazing," John conceded.

"You really think so?" Sherlock asked, sincerely pleased at the praise.

"Of course."

"Usually people don't think it's amazing," Sherlock said.

"Mad you discovered their secrets?" John asked.

"No. They think I used magic, so it isn't all that special. But I don't!" he said hotly. "I don't. That's no fun at all. I hate using magic, it makes everything too easy. That's why Mycroft calls me a Squib. I wish I lived with Muggles, it would be so much more interesting."

"It's not that exciting," John said. "I'd much rather live like this." He gestured at the train to indicate the Wizarding world.

"I'll grant you magic gives you more free time," Sherlock said, "more time to do what you really like. But Muggle crimes are so much more exciting than Wizarding crimes. If a Muggle was murdered in a room locked from the inside with no marks on the body, that's something. Here it's dull. They Apparated and used the Avada Kedavra curse. Dull, boring, waste of thought." He sat forward and lowered his voice, as though telling them a great secret. "I've been studying Muggles. That's how I knew how old your suitcase was and all. I want to know absolutely everything about them, because," he took a deep breath, "I want to be a detective for Muggles. I'll solve crimes better than any Muggle can, and I'll never use magic."