As they dragged him and Hermione along the corridor, Ron thought: there must be a way to escape. There must be a way out of here. We will get out of the bonds, and escape from the cell they put us in, and find Harry (who will, of course, still be alive), and defeat Voldemort. We must. We will.
Then they were in the cell and Voldemort was there, too, and all the plans silently collapsed.
"So, the other two points of the triangle," he said, and "The lower ones, of course", and various other things which passed Ron by entirely, because the blood banging in his head made it difficult to hear, and because he was busy formulating new plans.
"Avada kedavra," he muttered desperately, and was rewarded by a tiny spark of green from one finger, like the ghost of a firework.
Voldemort carried on laughing for some time. "Fool," he said, "as if anyone could cast the killing curse without a wand... but especially you," and this hurt Ron's pride, and he began casting every spell he could think of; curses, hexes, jinxes, Silencing Charms, and anything that would at least annoy Voldemort, even if it didn't actually do anything useful. After some hesitation, Hermione joined in. That more than doubled their firepower. Voldemort was indeed annoyed, and hexed them with a considerable blast of electricity.
He scoffed at them overbearingly for a while, but Hermione noted he had put up some rather strong Shielding Charms.
"I think a little more comfort would suit," he finally wound up, and lifted his wand. The cell suddenly bulged, grew, and merged with a second room like two mating soap bubbles.
Looking it over, Hermione concluded that the second room had not been an improvement. It was a dark, garish bedroom. The paintings on the walls were Surrealist, and gave a grim insight into Voldemort's age and mental state. The half-glimpsed statues and furniture were eerie monsters.
"You don't appreciate my bedchamber?" he leered at them. Hermione noted detachedly that the paucity of skin on his face meant he couldn't really smirk; every facial quirk came out as a grimace. The fact that Voldemort could not smile seemed strangely appropriate. She felt she might never manage another herself, for that matter.
"What do you say, Harry?" Voldemort asked casually over his shoulder. "Lumos," he appended, and a spotlight abruptly picked out Harry's figure from the darkness of the far wall. Ron and Hermione startled, feeling twin great surges of hope and terror, and waited for Harry to speak. He didn't.
Hermione, nonplussed, looked him up and down. He looked healthy, unharmed; he stood poised on a sort of wooden plinth, six inches high. He had no particular facial expression, although he looked perhaps a little surprised, with his lips slightly parted. Hermione waited for words to leave them. None did.
Voldemort strolled across to the far end of the chamber, still surrounded by his shields, and opened the door of a squat mahogany drinks cabinet. He serenely poured himself a whisky before finally asking "Well, Harry? Nothing to say?" and matter-of-factly plucking out Harry's right eyeball.
Hermione's scream at this point was appalling. Ron found he could only sob in agony as Voldemort tossed the glass eye up in the air, caught it, and popped it back into its socket. There was no blood to flow, no pus to make a mess. Voldemort had had Harry embalmed.
Ron found his voice at last, and roared things at Voldemort that he didn't hear, words he didn't even know. Voldemort ignored him, adjusting the glass eyes, making sure they both faced forwards.
Hermione, meanwhile, was silent. The shift from life to death had been too cruel and too quick. A moment ago: a seventeen-year-old boy, as beautiful as ever. Now: a thing, a dead thing, one that Voldemort seemed to consider a clever joke. With eyes of glass. Glass. Glass. Blue glass.
Hermione had a certain little green hope of which she had never spoken to anyone. Now, even as it curled and died, she registered the final insult: they hadn't even got the colour of the eyes right; and she would never see his real eyes again. The wandless Cruciatus felt as natural as tears, and blindsided Voldemort as he walked back across the room; and in the minutes that followed, it became clear that it had hurt Voldemort a lot more than he cared to admit, as he blasted the pair of them with every torturing spell he had ever known, and finished off with a particularly venomous bark of "Crucio!" at Hermione.
Ron would often wonder, in later life, exactly what Voldemort hoped to gain by that. Ron could have told him himself that Hermione was far too clever, and far too used to Cruciatus by that point, to be put out by such a trivial intrusion. While her body twitched and sparked and emitted raw, choked screams, her mind proceeded logically down the rather short list of spells that might serve her purpose in such a situation.
Ultimately, there was only one candidate; one that appealed both to her self-preservation, and her sense of justice. Hoping the screams would cover any noise, she sounded the words out in her head with a crispness worthy of McGonagall; Inferius Anime!
Harry's body jerked, shook its limbs experimentally, and climbed down off its plinth.
I thought he was supposed to have a power that the Dark Lord knew not, thought Ron as he watched the Inferius shuffle across the room. It can't very well be zombification, so it must be... He thought it over, and swallowed: oh. Love. Well, never mind, he thought, Hermione's got enough for both of us; just as Harry brought the plinth down on Voldemort's head, smashed his skull to pieces, and fulfilled the prophecy.