'What we need,' said Dumbledore slowly, and his light-blue eyes moved from Harry to Hermione, 'is more time.'

'But –' Hermione began. And then her eyes became very round. 'OH!'

'Now pay attention,' said Dumbledore, speaking very low, and very clearly. 'Sirius is locked in Professor Flitwick's office on the seventh floor. Thirteenth window from the right of the West Tower. If all goes well, you will be able to save more than one innocent life tonight. But remember this, both of you. You must not be seen. Miss Granger, you know the law – you know what is at stake … you – must – not – be – seen.'

Harry didn't have a clue what was going on. Dumbledore had turned on his heel and looked back as he reached the door.

'I am going to lock you in. It is –' he consulted his watch, 'five minutes to midnight. Miss Granger, three turns should do it. Good luck.'

'Three turns?' Harry repeated blankly, staring after Dumbledore's retreating form. 'Hermione, what –?'

But she was already reaching down the front of her robes to pull out what looked like a small hourglass on a gold chain around her neck, muttering feverishly all the while, 'Oh, it better work, I hope … I hope this works …'

'What are you –?' Harry began, but Hermione said impatiently, 'Harry, come over here quick!' He moved over and she draped the gold chain over his neck as well. Then she took the hourglass and turned it over once – twice – three times …

Everything began to spin. Hermione grabbed Harry's hand to stop him slipping the chain off over his head; he winced and looked around, but the spinning made him feel dizzy; he shut his eyes and when he opened them, the spinning had stopped and they were standing in the Entrance Hall.

'Come on, Harry!' Hermione whispered, whipping the chain off his shoulders and dragging him into a nearby broom cupboard.

'Look, Harry,' she said urgently. 'This –' she showed him the hourglass '– is a Time-Turner. That's how I've been getting to all my classes – by turning back time. If it worked, we've now gone three hours back in time. I think Dumbledore wants us to rescue Sirius on Buckbeak, you know, by flying him up to the tower …'

'"If it worked?"' Harry frowned, staring at the Time-Turner. 'You've been using it all year; what could go wrong now?'

'Don't ask,' Hermione said distractedly, looking at her watch. 'Where were we three hours ago? … We had the Cloak on and we were going down to Hagrid's …' She closed her eyes for a moment, then opened them and continued: 'We should have passed here by now, oh, I just hope this works …'

She pushed the door of the broom cupboard open and grabbed Harry, who was trying to make sense of all this, towards the castle's doors. Together they tugged them open, and Hermione gasped in horror.

It was raining. Cold, wet drops of rain were falling in sheets, onto the grounds, onto the Quidditch pitch, onto Hagrid's hut, and onto the castle's front steps.

'But this can't be right!' Hermione cried frantically, slamming the doors shut again and leaning against them as if determined to blot them out. 'It wasn't even cloudy three hours ago!'

'Where – when are we?'

'That's just it, I don't know,' she said, breathing hard as she looked at Harry. 'Oh, why didn't I say so … The Time-Turner's been malfunctioning for days, taking me too far back … I should have told Professor McGonagall, but I didn't, and – Oh, Harry, it's all my fault!' she cried.

'Well,' said Harry cautiously, after taking some time to digest all this, 'the first thing we should do is find out when we are. Then I suppose we can ask Dumbledore or McGonagall to send us back …'

'We can't ask anyone for help, Harry!' Hermione wailed. 'Professor McGonagall showed me loads of stuff that happened to people who meddled with time! We've got to be careful!'

'OK, OK, it was just an idea! How the heck are we supposed to get back if we can't do it by ourselves and nobody else knows who we are?'

'Harry, keep your voice down,' Hermione begged. 'We'd better go into the Great Hall before somebody finds us … It's a good thing we're wearing school robes,' she added. 'We'll look inconspicuous.'

They entered the Great Hall. It appeared to be just after dinner; the teachers had left and around twenty students remained, some talking, others bemoaning the amount of homework they had been set …

'POTTER!'

Both Harry and Hermione jumped. Professor McGonagall was striding into the Great Hall, livid with rage, a small first-year panting nervously behind her, but she wasn't heading for Harry; rather, towards a clump of people near the Gryffindor table –

Harry and Hermione looked at each other, and then casually walked over. Harry's heart nearly stopped when he saw who Professor McGonagall had been yelling at.

Two black-haired boys, about his own age, had apparently been staging a mock duel: both had their wands out and were pointing them at a round Slytherin boy who looked perfectly normal, apart from the fact that his terrified face and head were twice their normal size. The first black-haired boy had hazel eyes and round spectacles, and his messy hair stuck up at the back, just like Harry's. The second boy's hair was longer, and he was handsomer, but both James Potter and Sirius Black had an insolent, Fred-and-George-ish look about them as they turned to face Professor McGonagall.

'Potter! And you, Black! How dare you!' Professor McGonagall shrieked, bearing down upon the guilty pair. 'How dare you use an illegal hex! Twenty points from Gryffindor and double detention for the pair of you!' Then she turned to the hexed Slytherin and said in a slightly calmer, though brusque tone, 'You'd better get off to the hospital wing, Aubrey, that looks bad. Miss Bobbin, if you could help him …'

Harry watched as a Slytherin girl with long blonde hair went over to Aubrey and murmured in his ear as they left, 'It's all right, Bertram … Madam Pomfrey'll fix it in no time and then we can get back at Potter and his mates …'

'Gits,' said a voice so close to Harry's ear that he started; the boy next to him, a sallow, stringy Slytherin, was looking at James and Sirius with an expression of extreme distaste on his face. The red-haired girl standing at his side shrugged non-committally.

'Forget it, Sev,' she told him lightly, 'they're just a couple of bigheads. Goodbye,' she added, as she turned to leave the Hall, 'I've got that Slug Club meeting with Professor Slughorn, I just remembered.'

'Bye, Lily,' said the boy gloomily. He was still eyeing the two boys. Harry turned to see Hermione tugging at his arm. 'Yes, Hermione?'

'We need to talk. Come on,' she said, and she half-walked, half-ran out of the Great Hall, Harry sprinting after her.

'Where?' Harry asked, panting, as he caught up. Habit brought them to the portrait of the Fat Lady, which was the entrance to Gryffindor Tower. She frowned down at them.

'Password?' she asked.

'Fiat lux,' Harry said confidently, without thinking.

She knit her eyebrows together. 'Where have you been? Not even close.' Before Harry could reply, Hermione pinched him so hard he yelped in pain before he realised what she was on about. 'Bye,' he said hurriedly, as the Fat Lady looked after them, bemused.

'C'mon!' Hermione said as Harry glanced back at the Fat Lady. 'We need to find somewhere to talk.' She made sure no one was near and then lowered her voice. 'We can't go in there, obviously; and it's not as if we can just sprint into the nearest bathroom …' Her voice trailed off as she put her hand to her mouth.

'What?' asked Harry, but he already knew.

'Moaning Myrtle's bathroom,' they said together, and then set off for the second floor, watching for students as they went.

A/N: The italicised quote at the beginning of this story is taken directly from Harry Potter and the Prisoner of Azkaban (Chapter 21: Hermione's Secret).