Who is Paul Caldwell from The Egyptologist and what is their importance?

Paul Caldwell is the illegitimate son of Barnabas Davies, a rich man who wants all his illegitimate children to change their names to Davies. Harold Ferrell, an Australian detective hired by Davies, tracks down Paul's mother in Sydney and learns his story from there. Paul grows up in poverty and learns to pick pockets. He joins a circus where he does a minor act and picks pockets, for which he is arrested. Paul works out a deal with the police to join the military rather than serve jail time in exchange for information about Sydney Communists, information that he had gained through the friendship of Catherine Barry, a librarian. Catherine provides books on ancient Egypt and Egyptology to Paul because he has developed interest in the subject.