Chapter 2 - the one where he and Sirius tried to 'steal' potion ingredients from Lily but forgot she was teaching the seventh years.
It started within the first week of him coming to Hogwarts. Charlie and Sirius had hit it off like a bomb explosion (a glorious reaction for them and a disaster for everyone else) and they'd come up with quite an ingenious prank to pull on the poor unsuspecting students that were supposed to be under their care. But first they needed potions ingredients and in their fit of excitement forgot that Lily was teaching the seventh years and that they'd have to walk through her classroom to get to the store cupboard.
"What are you two up to?" Lily frowned.
"Nothing," Charlie said a little too quickly. Sirius beamed.
"Oh for the love of...please tell me you haven't corrupted him already Professor Black?!" Lily asked exasperatedly. Hermione snorted at that before either of them could answer. Charlie frowned curiously at her.
"Something to say Miss Granger?" Sirius asked innocently enough. Except that she'd known the man on far more familial terms for seven years now since she'd been staying over at Harry's practically every holiday they'd had since she'd started Hogwarts.
"No Sir, not really," Hermione said, a small shake of her head and a little smirk on her face.
"Please, share what's so amusing with the rest of the class Miss Granger..." Sirius smirked back at her.
"Professor Weasley doesn't need corrupting. Fred and George were his fault and a man who can create pranksters like that doesn't need leading astray, you just found him wandering in the same place you were," Hermione said.
"What makes you think I'm that bad?" Charlie fixed his blue eyes on Hermione's deep chocolate brown ones and her smile grew a little more devious.
"Well, my first clue was seven years ago, before I'd ever met you. I got it from a guy called Norbert, although if I recall he turned out to be more of a girl...Norberta, right?" Hermione raised an eyebrow and waited for his response. Charlie's face broke out into a wide smile.
"What about that screamed irresponsible to you?" He asked.
"Seriously?!" Hermione scoffed. "At no point in your response to three first years did you ask how or why we came to...have met Norbert. And there was no authoritative tone to it, not even one reprimanding sentence. Just a 'thanks for the letter, sounds great, shouldn't be a problem so long as we don't get caught. Let me know if the...logistics are a problem.'"
"Who is Norbert?" Lily and Sirius asked at the same time.
"A special friend of Hagrid's," Hermione answered and both Professors grimaced a little.
"We don't want to know, do we?" Lily sighed.
"No, sorry..." Hermione shook her head apologetically.
It was that small conversation that sparked Charlie's interest in Hermione and he tried to squash it, really really hard. But it wouldn't go away, like the persistent buzz of a fly or a nagging ache in the back of his head. And over the course of the school year it just grew louder and louder the more interactions he had with her.