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

The desire for Christianity is a central theme in the book. There are a large number of the characters who are seeking the peace of Christianity, though many of them don't know what they're looking for. Marcellus is one of those as the story opens and later comes to recognize that longing in others. For example, when he arrives at Arpina, he encounters the landowner - Kaeso. Kaeso is a wealthy man who is always angry. He yells at everyone and has no interest in being part of his son's life. The first time Marcellus meets him, he refuses to work as a scrivener. Then Marcellus tells Kaeso outright that he's searching for something. Marcellus is correct in that assumption and probably recognized it because he himself had recently been in the same situation.