Why does the reader care about Eustace at this point?  Partly because the other characters do, but mostly because we’ve seen the world through his eyes, and the world he sees is so colorless.  He thinks anything that causes him discomfort is caused by the people around him (whether because they’re “ignorant” or just “evil”).  As a result, he always ends up pushing people away.  It’s a lonely way to live, and he finally realizes it this chapter – when he may have lost his chance to change his way of life forever.

“Confound the fellow,” said Edmund.  “What on earth did [Eustace] want to slink away like this for?”

“But we must do something,” said Lucy.  “He may have got lost, or fallen into a hole, or been captured by savages.”

“Or killed by wild beasts,” said Drinian.

“And a good riddance if he has, I say,” muttered Rhince.

“Master Rhince,” said Reepicheep, “you never spoke a word that became you less.  The creature is no friend of mine but he is of the Queen’s blood, and while he is one of our fellowship it concerns our honor to find him and to avenge him if he is dead.”

“Of course we’ve got to find him (if we can),” said Caspian wearily.  “That’s the nuisance of it.  It means a search party and endless trouble.  Bother Eustace.”

Meanwhile, Eustace encounters a dragon (although he couldn’t name it as such; he doesn’t read the right books for that).  He at least has sense enough not to try to run away from a giant winged beast, and it turns out it’s a very old dragon.  He watches it take its last breath and die.

The relief was so great that Eustace almost laughed out loud.  He began to feel as if he had fought and killed the dragon instead of merely seeing it die.

When a thunderstorm starts up, he retreats to the dragon’s cave for shelter and (naturally) discovers its treasure.

Eustace (unlike most boys) had never thought much of treasure but he saw at once the use it would be in this new world which he had so foolishly stumbled into through the picture in Lucy’s bedroom at home.  “They don’t have any tax here,” he said, “and you don’t have to give treasure to the government.  With some of this stuff I could have quite a decent time.”

He fills his pockets and puts a bracelet on his arm, and then he falls asleep on the treasure.  But when he wakes up in the middle of the night, he (slowly) makes a shocking discovery:

He had turned into a dragon while he was asleep.  Sleeping on a dragon’s hoard with greedy, dragonish thoughts in his heart, he had become a dragon himself.

[…]

In spite of the pain, his first feeling was one of relief.  There was nothing to be afraid of any more.  He was a terror himself now and nothing in the world but a knight (and not all of those) would dare to attack him.  He could get even with Caspian and Edmund now –

But the moment he thought this he realized that he didn’t want to.  He wanted to be friends.  He wanted to get back among humans and talk and laugh and share things.  He realized that he was a monster cut off from the whole human race.  An appalling loneliness came over him.  He began to see that the others had not really been fiends at all.  He began to wonder if he himself had been such a nice person as he had always supposed.

Eustace got everything he ever wanted – and realized how empty it all was.  It takes him becoming a literal monster to finally consider the possibility that he might not be as amazing a person as he thought – to realize that he had made mistakes, and to regret those mistakes.  He’s come to the point of repentance, and he hardly even has a hope for a new life, but he goes back to find the others anyway, determined to make them understand what happened to him.

Next time: The adventure concludes…