Development of Dell Duke

In the beginning of the book, Dell was a big man. He had a set way of living, and it was lazy. He didn't do much t his job, and his home was messy. He sorted the kids he worked with into the four categories of the strange: the weirdos, the oddballs, the misfits, and the lone wolves.
Toward the middle of the book, Dell became a lot more passionate and caring. He had Willow to care for, and it challenged him to grow. He allowed his home to be taken over, and he went out of his way everyday to care for Willow. He even started running to try and become healthier
Toward the end of the book, Dell was frustrated. He was stressed from all the sacrifices he was making, and his body was sore. One morning he crashed his car, scratching it up against a fence. Then, trying to get out of his now damaged car, he hit a district owned van with his car door, scratching it too. As he walked away in embarrassment, his cat who was missing jumped between his legs. Looking at the dirty, scared animal something clicked in Dell's mind. He had to start taking more responsibility for his actions. After that, he had a spring in his step. It could've been the running, or just knowing he had done right by his cat, but from there forward he did things with happiness and integrity.

Development of Willow Chance

Willow Chance was naturally different than most. She was an only child, unable to fit into an easily identifiable ethnic category by sight, and adopted by a white couple. In the beginning of the book, she is obsessed with two things: plants and human diseases, or illnesses. She was very obviously extremely smart, to the extent that she was made fun off and seen as an odd ball. She lacked very much social understanding. 

Towards the middle of the book, when her parents passed away, she became very depressed. She no longer pointed out medical or plant related things. She was still very matter-a-fact about everything going on, but she was sad. She lacked her normal motivation and passion.

Towards the end of the book, she began finding a happy medium. She wasn't back to the same constant energetic spewing of facts, but she was enjoying working with plants again. She showed more feeling, and had more social understanding. She became more low-key, which I think is a sign of maturity. She still see's things objectively, but rather than being upset by them and or wanting to change them, she accepts the world as it is, and understands that everything isn't going to be perfect.