The Secrets of the Chamber of Secrets.
Just because they weren't friends anymore did not mean that Harry hadn't noticed something so seemingly impossible with Hermione; she was appearing from nowhere, and once his interest was piqued Harry had managed to get his hands on her timetable and discovered she was having classes at clashing times.
At first, he had just assumed she was attending the classes remotely, using one of those communication mirrors he had learnt about, set to record the lessons so then she could study under her own time, but that was quickly thrown out of the window when he remembered her appearing from nowhere not once, but a dozen times over, and how she appeared to be getting more and more tired….
For a week, Harry studied Hermione's movements and once or twice, he noticed her surreptitiously stuff something like an elaborate necklace into her robes. One day, Harry waited for her to come back from the library. He was waiting under a notice-me-not charm near the top of the steps leading close to Gryffindor tower; Hermione might have found a way to be in two or three places at once since her insane schedule gave her the chance to do that, but she hadn't changed that much. Some of her old habits still kept.
Harry waited for two hours before finally Hermione appeared, and one look at her face told him she was absolutely exhausted but was still lugging some heavy books around. While they weren't friends anymore, a part of Harry wished she would use magic to lift things like books unless she was trying to become a weightlifter, and once look at her tired face worried him. What the hell was she doing that would make her this exhausted?
Hermione slowly walked up the steps, each step measured and showing her clear fatigue. Harry waited until she was walking past him before she cast a mild sleeping charm on her. She was out like a light instantly.
Gently he grabbed her and lowered her to the ground, and pulled her into an alcove where it was unlikely she would be disturbed; with a bit of luck, Hermione would wake up on her own, and even with her clear memory of recall it would have taken a battering with all of her fatigue, so she'd hopefully believe she had felt so sleepy she had opted to walk to a quiet corner and simply fall asleep. This part of the school was Gryffindor country, so if she was found it would hopefully be by another Gryffindor
Harry flicked his wand, scanning for powerful magical artefacts, and two patches on Hermione's body lit up; the one over her right sleeve didn't interest him, since he knew it would be where she would keep her wand, but the one on her chest interested her; Harry gently knelt down, gently undoing the buttons around Hermione's neck, his fingers brushing her smooth soft skin, looking for a chain; in the time's Harry had seen Hermione appear out of nowhere, he had seen the glint of a chain.
He found it and gently hooped his finger around it and pulled it, and he pulled out a small, elaborate piece of jewellery that had a very small, delicate-looking hourglass. Harry examined it with his fingers for a moment, knowing from his last few years in the magical world knowing only too well how dangerous some artefacts were, memorising every detail before he simply slid it back. Just as he was standing upright, Harry looked down at Hermione again; he hadn't liked her attitude last year, but he still cared about her more than he did with Weasley. He flicked his wand, casting a timed sleeping spell to give her at least 2 hours of sleep.
And then he was gone.
X
Since the discovery, the Dementors were here because of Sirius Black, and Black was here because of him, Harry had learnt it was very hard for him to get to the Chamber of Secrets; he was still annoyed with Fudge's lack of common sense so he could tell Harry what was going on and why Black wanted to kill him, and none of the teachers respected how old he was now to give him pointers and advice. They seemed content with following him around, and so he'd needed to find ways of leaving Gryffindor Tower and to the corridor where the entrance was, scanning for tracking charms and surveillance spells along the way.
Armed with the image of the artefact Hermione was wearing around her neck, Harry walked into the Chamber library and he looked around the book titles, finding several likely candidates before he pulled a few off the shelves…
Harry was in the library for only two hours, looking through each book he could find before he found the right picture; the book edition was old, preserved by the Chamber's magic, so the picture was good quality and while it was clearly a different design and make, there were enough similarities for him to see this object was identical enough to the one Hermione had around her neck.
A Time Turner.
After reading the description of what the Time Turner did, Harry was amazed. A magical time machine; okay, granted, it only had a limited range of just a few days or hours, depending on its design, but it was still simply impressive and awesome. Once he had gone over the properties of a Time Turner, Harry had known this would be a great way for him to learn more about magic, and to have fun. The only problem was how was he going to get hold of a Time Turner? He couldn't steal it; from what he could tell, even in Slytherin's time, there was already enough talk about the paradoxes of time travel causing enough harm to warrant them being banned or locked up, except in extreme circumstances, and the wizarding world had likely not changed enough for that.
