that's your criticism of The Da Vinci Code? For me, it starts with the dude who stopped talking to his last-bloodline-of-Jesus granddaughter for 20 years over a misunderstanding but then spends his last 20 minutes stumbling from room to room writing secret messages in his own blood and entrails that only she can interpret.
But again, it's basically a framing reference for Holy Blood, Holy Grail, thereby tricking a whole new generation of the gullible to read illuminati conspiracy theories and profiting off the process. I mean, Brown went as far as naming the antagonist, Leigh Teabing, after an anagram of Holy Blood, Holy Grail authors Michael Baigent and Richard Leigh.
"It is typical of my unregenerable soul that I can only see this as a marvellous theme for a novel" - Anthony Fucking Burgess, setting up Da Vinci Code in 1982