Dan Brown will bring back his most famous character in a new novel coming later this year.

Doubleday will publish The Secret of Secrets in the fall, the press announced in a news release. It will be Brown’s sixth novel featuring Robert Langdon, a Harvard professor and symbology expert, and his first novel for adults in eight years.

Brown introduced Langdon in the 2000 novel Angels & Demons. Three years later, Langdon returned in The Da Vinci Code, a massive hit that spent more than two years on the New York Times bestseller list.

Brown brought back the character in the novels The Lost Symbol, Inferno, and Origin, all bestsellers. The Da Vinci Code, Angels & Demons, and Inferno were all adapted into films directed by Ron Howard and starring Tom Hanks; a series adaptation of The Lost Symbol streamed on Peacock in 2021.

The Secret of Secrets, Doubleday says, follows Langdon on the trail of his girlfriend, a scientist who has disappeared along with the manuscript for her controversial book.

Brown announced his new novel on Good Morning America, saying, “Thank you to all of my readers for your incredible patience waiting for this novel, which I realize took a while for me to complete, but there is a reason for that. I can now tell you that The Secret of Secrets is by far the most intricately plotted and ambitious book that I have ever written—and I also happen to think it is the most fun.”

The Secret of Secrets is slated for publication on Sept. 9.

Michael Schaub is a contributing writer.