Was this why Dumbledore would no longer meet Harry's eyes? Did he expect to see Voldemort staring out of them, afraid, perhaps, that their vivid green might turn suddenly to scarlet, with catlike slits for pupils? Harry remembered how the snakelike face of Voldemort had once forced itself out of the back of Professor Quirrell's head and ran his hand over the back of his own, wondering what it would feel like if Voldemort burst out of his skull.

He felt dirty, contaminated, as though he were carrying some deadly germ, unworthy to sit on the Underground train back from the hospital with innocent, clean people whose minds and bodies were free of the taint of Voldemort . . . he had not merely seen the snake, he had been the snake, he knew it now . . .

A truly terrible thought then occurred to him, a memory bobbing to the surface of his mind, one that made his insides writhe and squirm like serpents.

What's he after, apart from followers?

Stuff he can only get by stealth . . . like a weapon. Something he didn 't have last time.

I 'm the weapon, Harry thought, and it was as though poison were pumping through his veins, chilling him, bringing him out in a sweat as he swayed with the train through the dark tunnel. I'm the one Voldemort's trying to use, that's why they've got guards around me everywhere I go, it's not for my protection, it's for other people's, only it's not working, they can't have someone on me all the time at Hogwarts . . . I did attack Mr Weasley last night, it was me. Voldemort made me do it and he could be inside me, listening to my thought's right now — '

'Are you all right, Harry, dear?' whispered Mrs Weasley, leaning across Ginny to speak to him as the train rattled along through its dark tunnel. 'You don't look very well. Are you feeling sick?'

They were all watching him. He shook his head violently and stared up at an advertisement for home insurance.

'Harry, dear, are you sure you're all right?' said Mrs Weasley in a worried voice, as they walked around the unkempt patch of grass in the middle of Grimmauld Place. 'You look ever so pale . . . are you sure you slept this morning? You go upstairs to bed right now and you can have a couple of hours of sleep before dinner, all right?'

He nodded; here was a ready-made excuse not to talk to any of the others, which was precisely what he wanted, so when she opened the front door he hurried straight past the trolls-leg umbrella stand, up the stairs and into his and Ron's bedroom.

Here, he began to pace up and down, past the two beds and Phineas Nigellus's empty picture frame, his brain teeming and seething with questions and ever more dreadful ideas.

How had he become a snake? Perhaps he was an Animagus . . . no, he couldn't be, he would know . . . perhaps Voldemort was an Animagus . . . yes, thought Harry, that would fit, he would turn into a snake of course . . . and when he's possessing me, then we both transform . . . that still doesn't explain how I got to London and back to my bed in the space of about five minutes . . . but then Voldemort's about the most powerful wizard in the world, apart from Dumbledore, it's probably no problem at all to him to transport people like that.

And then, with a terrible stab of panic, he thought, but this is insane — if Voldemort 's possessing me, I 'm giving him a clear view into the Headquarters of the Order of the Phoenix right now! He 'll know who 's in the Order and where Sirius is . . . and I 've heard loads of stuff I shouldn 't have, everything Sirius told me the first night I was here . . .

There was only one thing for it: he would have to leave Grimmauld Place straightaway. He would spend Christmas at Hogwarts without the others, which would keep them safe over the holidays at least . . . but no, that wouldn't do, there were still plenty of people at Hogwarts to maim and injure. What if it was Seamus, Dean or Neville next time? He stopped his pacing and stood staring at Phineas Nigellus's empty frame. A leaden sensation was settling in the pit of his stomach. He had no alternative: he was going to have to return to Privet Drive, cut himself off from other wizards entirely.

Well, if he had to do it, he thought, there was no point hanging around. Trying with all his might not to think how the Dursleys were going to react when they found him on their doorstep six months earlier than they had expected, he strode over to his trunk, slammed the lid shut and locked it, then glanced around automatically for Hedwig before remembering that she was still at Hogwarts — well, her cage would be one less thing to carry — he seized one end of his trunk and had dragged it halfway towards the door when a snide voice said, 'Running away, are we?'

He looked around. Phineas Nigellus had appeared on the canvas of his portrait and was leaning against the frame, watching Harry with an amused expression on his face.

'Not running away, no,' said Harry shortly, dragging his trunk a few more feet across the room.

'I thought,' said Phineas Nigellus, stroking his pointed beard, 'that to belong in Gryffindor house you were supposed to be brave? It looks to me as though you would have been better off in my own house. We Slytherins are brave, yes, but not stupid. For instance, given the choice, we will always choose to save our own necks.'

'It's not my own neck I'm saving,' said Harry tersely, tugging the trunk over a patch of particularly uneven, moth-eaten carpet right in front of the door.

'Oh, I see,' said Phineas Nigellus, still stroking his beard, 'this is no cowardly flight — you are being noble. '

Harry ignored him. His hand was on the doorknob when Phineas Nigellus said lazily, 'I have a message for you from Albus Dumbledore.'

Harry span round.

'What is it?'

' "Stay where you are." '

'I haven't moved!' said Harry, his hand still upon the doorknob. 'So what's the message?'

'I have just given it to you, dolt,' said Phineas Nigellus smoothly. 'Dumbledore says, "Stay where you are." '

'Why?' said Harry eagerly, dropping the end of his trunk. 'Why does he want me to stay? What else did he say?'

'Nothing whatsoever,' said Phineas Nigellus, raising a thin black eyebrow as though he found Harry impertinent.

Harry's temper rose to the surface like a snake rearing from long grass. He was exhausted, he was confused beyond measure, he had experienced terror, relief, then terror again in the last twelve hours, and still Dumbledore did not want to talk to him!

'So that's it, is it?' he said loudly. '"Stay where you are" ? That's all anyone could tell me after I got attacked by those Dementors, too! Just stay put while the grown-ups sort it out, Harry! We won't bother telling you anything, though, because your tiny little brain might not be able to cope with it!'

'You know,' said Phineas Nigellus, even more loudly than Harry, 'this is precisely why I loathed being a teacher! Young people are so infernally convinced that they are absolutely right about everything. Has it not occurred to you, my poor puffed-up popinjay, that there might be an excellent reason why the Headmaster of Hogwarts is not confiding every tiny detail of his plans to you? Have you never paused, while feeling hard-done-by, to note that following Dumbledore's orders has never yet led you into harm? No. No, like all young people, you are quite sure that you alone feel and think, you alone recognise danger, you alone are the only one clever enough to realise what the Dark Lord may be planning — '

'He is planning something to do with me, then?' said Harry swiftly.

'Did I say that?' said Phineas Nigellus, idly examining his silk gloves. 'Now, if you will excuse me, I have better things to do than listen to adolescent agonising . . . good-day to you.'

And he strolled to the edge of his frame and out of sight.

'Fine, go then!' Harry bellowed at the empty frame. 'And tell Dumbledore thanks for nothing!'

The empty canvas remained silent. Fuming, Harry dragged his trunk back to the foot of his bed, then threw himself face down on the moth-eaten covers, his eyes shut, his body heavy and aching.

He felt as though he had journeyed for miles and miles . . . it seemed impossible that less than twenty-four hours ago Cho Chang had been approaching him under the mistletoe . . . he was so tired . . . he was scared to sleep . . . yet he did not know how long he could fight it . . . Dumbledore had told him to stay . . . that must mean he was allowed to sleep . . . but he was scared . . . what if it happened again?

He was sinking into shadows . . .

It was as though a film in his head had been waiting to start. He was walking down a deserted corridor towards a plain black door, past rough stone walls, torches, and an open doorway on to a flight of stone steps leading downstairs on the left . . .

He reached the black door but could not open it. . . he stood gazing at it, desperate for entry . . . something he wanted with all his heart lay beyond . . . a prize beyond his dreams . . . if only his scar would stop prickling . . . then he would be able to think more clearly . . .

'Harry,' said Ron's voice, from far, far away, 'Mum says dinners ready, but she'll save you something if you want to stay in bed.'

Harry opened his eyes, but Ron had already left the room.

He doesn't want to be on his own with me, Harry thought. Not after what he heard Moody say.

He supposed none of them would want him there any more, now that they knew what was inside him.

He would not go down to dinner; he would not inflict his company on them. He turned over on to his other side and, after a while, dropped back off to sleep. He woke much later, in the early hours of the morning, his insides aching with hunger and Ron snoring in the next bed. Squinting around the room, he saw the dark outline of Phineas Nigellus standing again in his portrait and it occurred to Harry that Dumbledore had probably sent Phineas Nigellus to watch over him, in case he attacked somebody else.

The feeling of being unclean intensified. He half-wished he had not obeyed Dumbledore . . . if this was how life was going to be for him in Grimmauld Place from now on, maybe he would be better off in Privet Drive after all.

*

Everybody else spent the following morning putting up Christmas decorations. Harry could not remember Sirius ever being in such a good mood; he was actually singing carols, apparently delighted that he was to have company over Christmas. Harry could hear his voice echoing up through the floor in the cold drawing room where he was sitting alone, watching the sky growing whiter outside the windows, threatening snow, all the time feeling a savage pleasure that he was giving the others the opportunity to keep talking about him, as they were bound to be doing. When he heard Mrs Weasley calling his name softly up the stairs around lunchtime, he retreated further upstairs and ignored her.