'Well, you can't,' said Harry shortly.

'You're being rather rude, you know,' said Luna serenely.

Harry swore and turned away. The very last thing he wanted now was a conversation with Luna Lovegood.

'Wait,' said Hermione suddenly. 'Wait . . . Harry, they can help.'

Harry and Ron looked at her.

'Listen,' she said urgently, 'Harry, we need to establish whether Sirius really has left Headquarters.'

'I've told you, I saw — '

'Harry, I'm begging you, please!' said Hermione desperately. 'Please let's just check that Sirius isn't at home before we go charging off to London. If we find out he's not there, then I swear I won't try to stop you. I'll come, I'll d — do whatever it takes to try and save him.'

'Sirius is being tortured NOW!' shouted Harry. 'We haven't got time to waste.'

'But if this is a trick of Voldemort's, Harry, we've got to check, we've got to.'

'How?' Harry demanded. 'How're we going to check?'

'We'll have to use Umbridge's fire and see if we can contact him, said Hermione, who looked positively terrified at the thought. 'We'll draw Umbridge away again, but we'll need lookouts, and that's where we can use Ginny and Luna.'

Though clearly struggling to understand what was going on, Ginny said immediately, 'Yeah, we'll do it,' and Luna said, 'When you say "Sirius", are you talking about Stubby Boardman?'

Nobody answered her.

'OK,' Harry said aggressively to Hermione, 'OK, if you can think of a way of doing this quickly, I'm with you, otherwise I'm going to the Department of Mysteries right now.'

'The Department of Mysteries?' said Luna, looking mildly surprised. 'But how are you going to get there?'

Again, Harry ignored her.

'Right,' said Hermione, twisting her hands together and pacing up and down between the desks. 'Right . . . well . . . one of us has to go and find Umbridge and — and send her off in the wrong direction, keep her away from her office. They could tell her — I don't know — that Peeves is up to something awful as usual . . .'

'I'll do it,' said Ron at once. 'I'll tell her Peeves is smashing up the Transfiguration department or something, it's miles away from her office. Come to think of it, I could probably persuade Peeves to do it if I met him on the way.'

It was a mark of the seriousness of the situation that Hermione made no objection to the smashing up of the Transfiguration department.

'OK,' she said, her brow furrowed as she continued to pace. 'Now, we need to keep students right away from her office while we force entry, or some Slytherin's bound to go and tip her off.'

'Luna and I can stand at either end of the corridor,' said Ginny promptly, 'and warn people not to go down there because someone's let off a load of Garrotting Gas.' Hermione looked surprised at the readiness with which Ginny had come up with this lie; Ginny shrugged and said, 'Fred and George were planning to do it before they left.'

'OK,' said Hermione. 'Well then, Harry, you and I will be under the Invisibility Cloak and we'll sneak into the office and you can talk to Sirius — '

'He's not there, Hermione!'

'I mean, you can — can check whether Sirius is at home or not while I keep watch, I don't think you should be in there alone, Lee's already proved the windows a weak spot, sending those Nifflers through it.'

Even through his anger and impatience, Harry recognised Hermione's offer to accompany him into Umbridge's office as a sign of solidarity and loyalty.

'I . . . OK, thanks,' he muttered.

'Right, well, even if we do all of that, I don't think we're going to be able to bank on more than five minutes,' said Hermione, looking relieved that Harry seemed to have accepted the plan, 'not with Filch and the wretched Inquisitorial Squad floating around.'

'Five minutes'll be enough,' said Harry 'C'mon, let's go — '

'Now?' said Hermione, looking shocked.

'Of course now!' said Harry angrily. 'What did you think, we're going to wait until after dinner or something? Hermione, Sirius is being tortured right now!'

'I — oh, all right,' she said desperately. 'You go and get the Invisibility Cloak and we'll meet you at the end of Umbridge's corridor, OK?'

Harry didn't answer, but flung himself out of the room and began to fight his way through the milling crowds outside. Two floors up he met Seamus and Dean, who hailed him jovially and told him they were planning a dusk-till-dawn end-of-exams celebration in the common room. Harry barely heard them. He scrambled through the portrait hole while they were still arguing about how many black-market Butterbeers they would need and was climbing back out of it, the Invisibility Cloak and Sirius's knife secure in his bag, before they noticed he had left them.

'Harry, d'you want to chip in a couple of Galleons? Harold Dingle reckons he could sell us some Firewhisky — '

But Harry was already tearing away back along the corridor, and a couple of minutes later was jumping the last few stairs to join Ron, Hermione, Ginny and Luna, who were huddled together at the end of Umbridge's corridor.

'Got it,' he panted. 'Ready to go, then?'

'All right,' whispered Hermione as a gang of loud sixth-years passed them. 'So Ron — you go and head Umbridge off . . . Ginny, Luna, if you can start moving people out of the corridor . . . Harry and I will get the Cloak on and wait until the coast is clear . . .'

Ron strode away, his bright-red hair visible right to the end of the passage; meanwhile Ginny's equally vivid head bobbed between the jostling students surrounding them in the other direction, trailed by Luna's blonde one.

'Get over here,' muttered Hermione, tugging at Harry's wrist and pulling him back into a recess where the ugly stone head of a medieval wizard stood muttering to itself on a column. 'Are — are you sure you're OK, Harry? You're still very pale.'

'I'm fine,' he said shortly, tugging the Invisibility Cloak from out of his bag. In truth, his scar was aching, but not so badly that he thought Voldemort had yet dealt Sirius a fatal blow; it had hurt much worse than this when Voldemort had been punishing Avery . . .

'Here,' he said; he threw the Invisibility Cloak over both of them and they stood listening carefully over the Latin mumblings of the bust in front of them.

'You can't come down here!' Ginny was calling to the crowd. 'No, sorry, you're going to have to go round by the swivelling staircase, someone's let off Garrotting Gas just along here — '

They could hear people complaining; one surly voice said, 'I can't see no gas.'

'That's because it's colourless,' said Ginny in a convincingly exasperated voice, 'but if you want to walk through it, carry on, then we'll have your body as proof for the next idiot who doesn't believe us.'

Slowly, the crowd thinned. The news about the Garrotting Gas seemed to have spread; people were not coming this way any more. When at last the surrounding area was quite clear, Hermione said quietly, 'I think that's as good as we're going to get, Harry — come on, let's do it.'

They moved forwards, covered by the Cloak. Luna was standing with her back to them at the far end of the corridor. As they passed Ginny, Hermione whispered, 'Good one . . . don't forget the signal.'

'What's the signal?' muttered Harry, as they approached Umbridge's door.

'A loud chorus of "Weasley is our King" if they see Umbridge coming,' replied Hermione, as Harry inserted the blade of Sirius's knife in the crack between door and wall. The lock clicked open and they entered the office.

The garish kittens were basking in the late-afternoon sunshine that was warming their plates, but otherwise the office was as still and unoccupied as last time. Hermione breathed a sigh of relief.

'I thought she might have added extra security after the second Niffler.'

They pulled off the Cloak; Hermione hurried over to the window and stood out of sight, peering down into the grounds with her wand out. Harry dashed over to the fireplace, seized the pot of Floo powder and threw a pinch into the grate, causing emerald flames to burst into life there. He knelt down quickly, thrust his head into the dancing fire and cried, 'Number twelve, Grimmauld Place!'

His head began to spin as though he had just got off a fairground ride though his knees remained firmly planted on the cold office floor. He kept his eyes screwed up against the whirling ash and when the spinning stopped he opened them to find himself looking out at the long, cold kitchen of Grimmauld Place.

There was nobody there. He had expected this, yet was not prepared for the molten wave of dread and panic that seemed to burst through his stomach at the sight of the deserted room.

'Sirius?' he shouted. 'Sirius, are you there?'

His voice echoed around the room, but there was no answer except a tiny scuffing sound to the right of the fire.

'Who's there?' he called, wondering whether it was just a mouse.

Kreacher the house-elf crept into view. He looked highly delighted about something, though he seemed to have recently sustained a nasty injury to both hands, which were heavily bandaged.

'It's the Potter boy's head in the fire,' Kreacher informed the empty kitchen, stealing furtive, oddly triumphant glances at Harry. 'What has he come for, Kreacher wonders?'

'Where's Sirius, Kreacher?' Harry demanded.

The house-elf gave a wheezy chuckle.

'Master has gone out, Harry Potter.'

'Where's he gone? Where 's he gone, Kreacher? '

Kreacher merely cackled.

'I'm warning you!' said Harry, fully aware that his scope for inflicting punishment upon Kreacher was almost non-existent in this position. 'What about Lupin? Mad-Eye? Any of them, are any of them there?'

'Nobody here but Kreacher!' said the elf gleefully, and turning away from Harry he began to walk slowly towards the door at the end of the kitchen. 'Kreacher thinks he will have a little chat with his mistress now, yes, he hasn't had a chance in a long time, Kreacher's master has been keeping him away from her — '

'Where has Sirius gone?' Harry yelled after the elf. 'Kreacher, has he gone to the Department of Mysteries? '

Kreacher stopped in his tracks. Harry could just make out the back of his bald head through the forest of chair legs before him.

'Master does not tell poor Kreacher where he is going,' said the elf quietly.

'But you know!' shouted Harry. 'Don't you? You know where he is!'

There was a moment's silence, then the elf let out his loudest cackle yet.

'Master will not come back from the Department of Mysteries!' he said gleefully. 'Kreacher and his mistress are alone again!'