I heard this was the one passage in The Lord of the Rings that made Tolkein cry when he re-read it (though I haven't verified this). It depicts Gollum's wrestling over whether or not to betray Frodo to the giant spider, Shelob. Ultimately, it describes the point of no return for Gollum's soul.

And so Gollum found them hours later, when he returned, when he returned, crawling and creeping down the path of gloom ahead.  Sam sat propped against the stone, his head dropping sideways and his breathing heavy.  In his lap lay Frodo's head, drowned deep in sleep; upon his white forehead lay one of Sam's brown hands, and the other lay softly upon his master's breast.  Peace was in both their faces.

Gollum looked at them.  A strange expression passed over his lean hungry face.  The gleam faded from his eyes, and they went dim and grey, old and tired.  A spasm of pain seemed to twist him, and he turned away, peering back up towards the pass, shaking his head, as if engaged in some interior debate.  Then he came back, and slowly putting out a trembling hand, very cautiously he touched Frodo's knee - but almost the touch was a caress.  For a fleeting moment, could one of the sleepers have seen him, they would have thought that they beheld an old weary hobbit, shrunken by the years that had carried him far beyond his time, beyond friends and kin, and the fields and streams of youth, an old starved pitiable thing.

But at that touch Frodo stirred and cried out softly in his sleep, and immediately Sam was wide awake.  The first thing he saw was Gollum - 'pawing at master,' as he thought.

'Hey you!' he said roughly.  'What are you up to?'

'Nothing, nothing,' said Gollum softly.  'Nice Master!'

'I daresay,' said Sam.  'But where have you been to - sneaking off and sneaking back, you old villain?'

Gollum withdrew himself, and a green glint flickered under his heavy lids.  Almost spider-like he looked now, crouched back on his bent limbs, with his protruding eyes.  The fleeting moment had passed, beyond recall.  (Tolkein, The Two Towers, p. 699)

This reminds me of Herod in Mark 6:20-21, 26.  As Herodias' window of opportunity to dispose of John arose, Herod's window of opportunity to receive the truth closed.