What are the motifs in Holy Blood, Holy Grail by Michael Baigent?

Religious heresies were quite common in the early days of Christianity and proved to be a thorn in Rome's side throughout much of Rome's history. Heresy is defined as religious beliefs that go against the teachings of the Bible. There have been many heresies throughout history and some of the core beliefs of these heresies have led credence to the authors' conclusion.