In Chapter 16 through 19, we see the ways in which Nick has grown. How has he changed?

When we first met Nick, he would hesitate and was unsure of himself. Over the course of the story, however, we find him willing to help Smoke in spite of the fact that everyone thinks he's guilty. He also discusses his opinions with his parents and Marta, but he does not let them sway him, as he has come to trust his own instincts.