Thanks to the The Dan Brown Sequel Generator from the folks at Slate, I can, much like the proverbial monkey working at a typewriter, help him along by putting together the outline of his next book, this time set in New York City, and involving (CENSORED):
A mysterious puzzle at the heart of New York City. A murderous cult determined to protect it. A frantic race to uncover (CENSORED)'s darkest secret.
The Divine Mark
When world-famous Harvard symbologist Robert Langdon is summoned to the Apollo Theater to analyze a mysterious geometric form—etched into the floor next to the mangled body of the head docent—he discovers evidence of the unthinkable: the resurgence of the ancient cult of the Baalinistas, a secret branch of (CENSORED) that has surfaced from the shadows to carry out its legendary vendetta against its mortal enemy, the Vatican.
Langdon's worst fears are confirmed when a messenger from the Baalinistas appears at the Empire State Building to deliver a macabre ultimatum: Deposit $1 billion in (CENSORED)'s off-shore bank accounts or the exclusive clothier of the Swiss Guards will be bankrupted. Racing against the clock, Langdon joins forces with the Amazonian and quick-witted daughter of the murdered docent in a desperate bid to crack the code that will reveal the cult's secret plan.
Embarking on a frantic hunt, Langdon and his companion follow a 1100-year-old trail through New York City's most venerable buildings and historic monuments, pursued by a Norwegian assassin the cult has sent to thwart them. What they discover threatens to expose a conspiracy that goes all the way back to Allen Ginsberg and the very founding of (CENSORED).