'He heard only the beginning, the part foretelling the birth of a boy in July to parents who had thrice defied Voldemort. Consequently, he could not warn his master that to attack you would be to risk transferring power to you, and marking you as his equal. So Voldemort never knew that there might be danger in attacking you, that it might be wise to wait, to learn more. He did not know that you would have power the Dark Lord knows not — '

'But I don't!' said Harry, in a strangled voice. 'I haven't any powers he hasn't got, I couldn't fight the way he did tonight, I can't possess people or — or kill them — '

'There is a room in the Department of Mysteries,' interrupted Dumbledore, 'that is kept locked at all times. It contains a force that is at once more wonderful and more terrible than death, than human intelligence, than the forces of nature. It is also, perhaps, the most mysterious of the many subjects for study that reside there. It is the power held within that room that you possess in such quantities and which Voldemort has not at all. That power took you to save Sirius tonight. That power also saved you from possession by Voldemort, because he could not bear to reside in a body so full of the force he detests. In the end, it mattered not that you could not close your mind. It was your heart that saved you.'

Harry closed his eyes. If he had not gone to save Sirius, Sirius would not have died . . . More to stave off the moment when he would have to think of Sirius again, Harry asked, without caring much about the answer, 'The end of the prophecy . . . it was something about . . . neither can live . . .'

'. . . while the other survives, ' said Dumbledore.

'So,' said Harry, dredging up the words from what felt like a deep well of despair inside him, 'so does that mean that . . . that one of us has got to kill the other one . . . in the end?'

'Yes,' said Dumbledore.

For a long time, neither of them spoke. Somewhere far beyond the office walls, Harry could hear the sound of voices, students heading down to the Great Hall for an early breakfast, perhaps. It seemed impossible that there could be people in the world who still desired food, who laughed, who neither knew nor cared that Sirius Black was gone for ever. Sirius seemed a million miles away already; even now a part of Harry still believed that if he had only pulled back that veil, he would have found Sirius looking back at him, greeting him, perhaps, with his laugh like a bark . . .

'I feel I owe you another explanation, Harry,' said Dumbledore hesitantly. 'You may, perhaps, have wondered why I never chose you as a prefect? I must confess . . . that I rather thought . . . you had enough responsibility to be going on with.'

Harry looked up at him and saw a tear trickling down Dumbledore's face into his long silver beard.