So, the authors of the Holy Blood and Holy Grail ("HBHG") are suing Dan Brown for using their plot for the blockbuster novel, the Da Vinci Code ("DVC"). No one would deny that DVC is based on HBHG, but can Brown be accused of plagiarism? If HBHG was marketed as a work of fiction, there would be no contest, but in fact it is claimed to be fact. For that reason, I'm not sure they can complain that their ideas have been used as they are not claiming the plot was the work of their imagination. They say they were merely uncovering facts that must then be in the public domain. Of course, the irony is that HBHG is fiction and the authors did make it up. It will be interesting to see if they will admit this to win the case.