Harry made to speak again, but this time Dumbledore raised his hand for silence, frowning slightly at the emerald liquid, evidently thinking hard.
“Undoubtedly,” he said, finally, “this potion must act in a way that will prevent me taking the Horcrux. It might paralyze me, cause me to forget what I am here for, create so much pain I am distracted, or render me incapable in some other way. This being the case, Harry, it will be your job to make sure I keep drinking, even if you have to tip the potion into my protesting mouth. You understand?”
Their eyes met over the basin, each pale face lit with that strange, green light. Harry did not speak. Was this why he had been invited along—so that he could force-feed Dumbledore a potion that might cause him unendurable pain?
“You remember,” said Dumbledore, “the condition on which I brought you with me?”
Harry hesitated, looking into the blue eyes that had turned green in the reflected light of the basin.
“But what if—?”
“You swore, did you not, to follow any command I gave you?”
“Yes, but—”
“I warned you, did I not, that there might be danger?”
“Yes,” said Harry, “but—”
“Well, then,” said Dumbledore, shaking back his sleeves once more and raising the empty goblet, “you have my orders.”
“Why can’t I drink the potion instead?” asked Harry desperately.
“Because I am much older, much cleverer, and much less valuable,” said Dumbledore. “Once and for all, Harry, do I have your word that you will do all in your power to make me keep drinking?”
“Couldn’t—?”
“Do I have it?”
“But—”
“Your word, Harry.”
“I—all right, but—”
Before Harry could make any further protest, Dumbledore lowered the crystal goblet into the potion. For a split second, Harry hoped that he would not be able to touch the potion with the goblet, but the crystal sank into the surface as nothing else had; when the glass was full to the brim, Dumbledore lifted it to his mouth.
“Your good health, Harry.”
And he drained the goblet. Harry watched, terrified, his hands gripping the rim of the basin so hard that his fingertips were numb.
“Professor?” he said anxiously, as Dumbledore lowered the empty glass. “How do you feel?”
Dumbledore shook his head, his eyes closed. Harry wondered whether he was in pain. Dumbledore plunged the glass blindly back into the basin, refilled it, and drank once more.
In silence, Dumbledore drank three gobletsful of the potion. Then, halfway through the fourth goblet, he staggered and fell forward against the basin. His eyes were still closed, his breathing heavy.
“Professor Dumbledore?” said Harry, his voice strained. “Can you hear me?”
Dumbledore did not answer. His face was twitching as though he was deeply asleep, but dreaming a horrible dream. His grip on the goblet was slackening; the potion was about to spill from it. Harry reached forward and grasped the crystal cup, holding it steady.
“Professor, can you hear me?” he repeated loudly, his voice echoing around the cavern.