She didn't hear the answer from inside the compartment, but after the boy opened the door, she did think she heard him say - unless she'd somehow misheard - "Does anyone here know the six quarks or where I can find a first-year girl named Hermione Granger?"
After the boy had closed that compartment door, Hermione said, "Can I help you with something?"
The scarfed face turned to look at her, and the voice said, "Not unless you can name the six quarks or tell me where to find Hermione Granger."
"Up, down, strange, charm, truth, beauty, and why are you looking for her?"
It was hard to tell from this distance, but she thought she saw the boy grin widely under his scarf. "Ah, so you're a first-year girl named Hermione Granger," said that young, muffled voice. "On the train to Hogwarts, no less." The boy started to walk towards her and her compartment, and his trunk slithered along after him. "Technically, all I needed to do was look for you, but it seems likely that I'm meant to talk to you or invite you to join my party or get a key magical item from you or find out that Hogwarts was built over the ruins of an ancient temple or something. PC or NPC, that is the question?"
Hermione opened her mouth to reply to this, but then she couldn't think of any possible reply to... whatever it was she'd just heard, even as the boy walked over to her, looked inside the compartment, nodded with satisfaction, and sat down on the bench across from her own. His trunk scurried in after him, grew to three times its former diameter and snuggled up next to her own in an oddly disturbing fashion.
"Please, have a seat," said the boy, "and do please close the door behind you, if you would. Don't worry, I don't bite anyone who doesn't bite me first." He was already unwinding the scarf from around his head.
The imputation that this boy thought she was scared of him made her hand send the door sliding shut, jamming it into the wall with unnecessary force. She spun around and saw a young face with bright, laughing green eyes, and an angry red-dark scar set into his forehead that reminded her of something in the back of her mind but right now she had more important things to think about. "I didn't say I was Hermione Granger!"
"I didn't say you said you were Hermione Granger, I just said you were Hermione Granger. If you're asking how I know, it's because I know everything. Good evening ladies and gentlemen, my name is Harry James Potter-Evans-Verres or Harry Potter for short, I know that probably doesn't mean anything to you for a change -"
Hermione's mind finally made the connection. The scar on his forehead, the shape of a lightning bolt. "Harry Potter! You're in Modern Magical History and The Rise and Fall of the Dark Arts and Great Wizarding Events of the Twentieth Century." It was actually the very first time in her whole life that she'd met someone from inside a book, and it was a rather odd feeling.
The boy blinked three times. "I'm in books? Wait, of course I'm in books... what a strange thought."
"Goodness, didn't you know?" said Hermione. "I'd have found out everything I could if it was me."
The boy spoke rather dryly. "Miss Granger, it has been less than 72 hours since I went to Diagon Alley and discovered my claim to fame. I have spent the last two days buying science books. Believe me, I intend to find out everything I can." The boy hesitated. "What do the books say about me?"
Hermione Granger's mind flashed back, she hadn't realised she would be tested on those books so she'd read them only once, but it was just a month ago so the material was still fresh in her mind. "You're the only one who's survived the Killing Curse so you're called the Boy-Who-Lived. You were born to James Potter and Lily Potter formerly Lily Evans on the 31st of July 1980. On the 31st of October 1981 the Dark Lord He-Who-Must-Not-Be-Named though I don't know why not attacked your home. You were found alive with the scar on your forehead in the ruins of your parents' house near the burnt remains of You-Know-Who's body. Chief Warlock Albus Percival Wulfric Brian Dumbledore sent you off somewhere, no one knows where. The Rise and Fall of the Dark Arts claims that you survived because of your mother's love and that your scar contains all of the Dark Lord's magical power and that the centaurs fear you, but Great Wizarding Events of the Twentieth Century doesn't mention anything like that and Modern Magical History warns that there are lots of crackpot theories about you."
The boy's mouth was hanging open. "Were you told to wait for Harry Potter on the train to Hogwarts, or something like that?"
"No," Hermione said. "Who told you about me?"
"Professor McGonagall and I believe I see why. Do you have an eidetic memory, Hermione?"
Hermione shook her head. "It's not photographic, I've always wished it was but I had to read my school books five times over to memorize them all."
"Really," the boy said in a slightly strangled voice. "I hope you don't mind if I test that - it's not that I don't believe you, but as the saying goes, 'Trust, but verify'. No point in wondering when I can just do the experiment."
Hermione smiled, rather smugly. She so loved tests. "Go ahead."
The boy stuck a hand into a pouch at his side and said "Magical Drafts and Potions by Arsenius Jigger". When he withdrew his hand it was holding the book he'd named.
Instantly Hermione wanted one of those pouches more than she'd ever wanted anything.
The boy opened the book to somewhere in the middle and looked down. "If you were making oil of sharpness -"
"I can see that page from here, you know!"
The boy tilted the book so that she couldn't see it any more, and flipped the pages again. "If you were brewing a potion of spider climbing, what would be the next ingredient you added after the Acromantula silk?"
"After dropping in the silk, wait until the potion has turned exactly the shade of the cloudless dawn sky, 8 degrees from the horizon and 8 minutes before the tip of the sun first becomes visible. Stir eight times widdershins and once deasil, and then add eight drams of unicorn bogies."
The boy shut the book with a sharp snap and put the book back into his pouch, which swallowed it with a small burping noise. "Well well well well well well. I should like to make you a proposition, Miss Granger."
"A proposition?" Hermione said suspiciously. Girls weren't supposed to listen to those.
It was also at this point that Hermione realised the other thing - well, one of the things - which was odd about the boy. Apparently people who were in books actually sounded like a book when they talked. This was quite the surprising discovery.
The boy reached into his pouch and said, "can of pop", retrieving a bright green cylinder. He held it out to her and said, "Can I offer you something to drink?"
Hermione politely accepted the fizzy drink. In fact she was feeling sort of thirsty by now. "Thank you very much," Hermione said as she popped the top. "Was that your proposition?"
The boy coughed. "No," he said. Just as Hermione started to drink, he said, "I'd like you to help me take over the universe."