They were back in Dumbledore’s office, the windows dark, and Fawkes sat silent as Snape sat quite still, as Dumbledore walked around him, talking.
“Harry must not know, not until the last moment, not until it is necessary, otherwise how could he have the strength to do what must be done?”
“But what must he do?”
“That is between Harry and me. Now listen closely, Severus. There will come a time—after my death—do not argue, do not interrupt! There will come a time when Lord Voldemort will seem to fear for the life of his snake.”
“For Nagini?” Snape looked astonished.
“Precisely. If there comes a time when Lord Voldemort stops sending that snake forth to do his bidding, but keeps it safe beside him under magical protection, then, I think, it will be safe to tell Harry.”
“Tell him what?”
Dumbledore took a deep breath and closed his eyes.
“Tell him that on the night Lord Voldemort tried to kill him, when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort’s soul was blasted apart from the whole, and latched itself onto the only living soul left in that collapsed building. Part of Lord Voldemort lives inside Harry, and it is that which gives him the power of speech with snakes, and a connection with Lord Voldemort’s mind that he has never understood. And while that fragment of soul, unmissed by Voldemort, remains attached to and protected by Harry, Lord Voldemort cannot die.”
Harry seemed to be watching the two men from one end of a long tunnel, they were so far away from him, their voices echoing strangely in his ears.
“So the boy… the boy must die?” asked Snape quite calmly.
“And Voldemort himself must do it, Severus. That is essential.”
Another long silence. Then Snape said, “I thought… all those years… that we were protecting him for her. For Lily.”
“We have protected him because it has been essential to teach him, to raise him, to let him try his strength,” said Dumbledore, his eyes still tight shut. “Meanwhile, the connection between them grows ever stronger, a parasitic growth. Sometimes I have thought he suspects it himself. If I know him, he will have arranged matters so that when he does set out to meet his death, it will truly mean the end of Voldemort.”