What is the main conflict in The Last Supper: A Novel by Charles McCarry?

The Last Supper by Charles McCarry follows the careers of three American intelligence agents, Hubbard Christopher and his son Paul, and their associate Barnabas "Barney" Wolkowicz from World War II through the Nixon years. At the end, Barney confesses to having been a Soviet agent all along and confirms Paul's growing suspicions of what has really taken place.