Robert Lewis is the man responsible for Rosa's death. Throughout the novel, Pancho is completely dedicated to finding and killing him to avenge his sister's murder. When he finally tracks Robert Lewis down, however, Pancho is unable to kill him. He knows that he would be throwing his life away and that Robert's death won't bring Rosa back. By sparing Robert Lewis' life, Pancho shows that he has completely transformed, maturing into a beautiful butterfly.
