The Secret of Secrets

Robert Langdon, esteemed professor of symbology, travels to Prague to attend a groundbreaking lecture by Katherine Solomon—a prominent noetic scientist with whom he has recently begun a relationship. Katherine is on the verge of publishing an explosive book that contains startling discoveries about the nature of human consciousness and threatens to disrupt centuries of established belief. But a brutal murder catapults the trip into chaos, and Katherine suddenly disappears along with her manuscript. Langdon finds himself targeted by a powerful organization and hunted by a chilling assailant sprung from Prague’s most ancient mythology. As the plot expands into London and New York, Langdon desperately searches for Katherine . . . and for answers. In a thrilling race through the dual worlds of futuristic science and mystical lore, he uncovers a shocking truth about a secret project that will forever change the way we think about the human mind.

The Secret of Secrets is a mystery thriller novel by American author Dan Brown and the sixth installment in his Robert Langdon series, following Origin. The book was released on September 9, 2025.

As of January 2026, the book has been featured on New York Times' best-seller list for 17 weeks in a row.