What is the theme in The Robe by Lloyd C. Douglas?

One main theme in the novel, The Robe, is that of faith. Over the course of the novel, Marcellus comes to accept Jesus Christ's teachings and his promise of everlasting life. He believes that as long as he stays true to his faith, God's kingdom will await him at his death. Thus, when faced with choosing to denounce his faith or die.... Marcellus happily dies, knowing eternity awaits him.