In Wyhdham's The Chrysalids, description of David's character at the beginning of the story, events that caused change, and his character at the end of the story.
At the start of John Wyndham's novel, The Chrysalids, David (the main character) is young and innocent. He is unaware of the deep significance of what takes place around him with regard to his culture's wish to wipe out the "mutants."
When David realizes that Sophie has an extra toe, he is not quite sure what all the fuss is about—particularly that he is sworn to secrecy.
It was so heavy a promise that I was quite resolved to keep it...Though, underneath, I was puzzled by its evident importance. It seemed a very small toe to cause such a degree of anxiety.
On his way home, some part of the society's teachings about "mutants" becomes clear, but still does not form a deep enough impression on David. The Sunday "precepts" connect...
...with a click that was almost audible...The Definition of Man recited itself in my head: '...each leg shall be jointed twice and have one foot, and each foot five toes, and each toe shall end with a flat nail...'
This small realization still does not quite impact the boy. David returns home and sees the same signs on the walls in his home that have always been there—but he has really never understood the context of these statements or how they impact others.
The nearest approach to decoration was a number of wooden panels with sayings, mostly from Repentances, artificially burnt into them. The one on the left of the fireplace read: ONLY THE IMAGE OF GOD IS MAN...KEEP PURE THE STOCK OF THE LORD...WATCH THOU FOR THE MUTANT!...Many of them were still obscure to me.
We see a distinct change in David when he is beaten for having knowledge of Sophie's condition and not reporting it. After his father is done with him, while his sister Mary dresses his wounds, David reflects on what has happened:
By now it was not so much the bodily hurts that brought [tears]: it was bitterness, self-contempt, and abasement...'I couldn't help it, Sophie,' I sobbed.
In being beaten, David told what he knew about Sophie and feels guilty—self-contempt; but the bitterness he experiences speaks to anger and resentment, against the world that has such laws, and a father who seemed not to hesitate in delivering his "torture" to force his knowledge from him, along with his punishment as well.
We now see a new David. He shares (telepathically) with his friends that what they have been taught is wrong—that Sophie was not a threat. The others struggle with this news, however...
You can't lie when you talk with your thoughts. [The others] wrestled with the novel idea...
Now David knows more of the world and he has passed his own judgment: his family and his society are wrong. David becomes an independent thinker.
The reader comprehends to what extent David has grown as the telepaths realize that they have been discovered. Alan knows everything his wife (Anne—a telepath) told him before she killed herself, and others are suspected. Michael tells David he must be prepared to kill if necessary to save them, and he must be especially responsible for Petra, as she is the weakest of them.
If worst comes to worst, and you can't save Petra, it would be kinder to kill her than let her go to sterilization and banishment to the Fringes—a lot more merciful for a child.
David understands and agrees. The next day he is called to act—they must flee. His strength of character allows the more mature David to lead his group away from civilization: escaping the Fringe people and finally finding safety with the Sealand people.