what does the butterfly mean at the end of the novel?

Both Jefferson and Grant have lessons to learn as one needs to teach the other and one needs to understand how the lesson should be taught. The butterfly, a symbol of maturity and growth, shows that indeed they have achieved their goals.

Grant is waiting in a field for Jefferson's execution. He chastises himself for not being there. Suddenly, his thoughts are interrupted by a yellow butterfly. It hovers briefly and then drifts towards the quarter. As he studies the butterfly Grant feels the execution is over. The butterfly might represent Jefferson in some way. He has shed his old pain and is born again, beautiful and free.