This thriller novel follows symbologist Robert Langdon and cryptographer Sophie Neveu as they investigate a murder in the Louvre Museum in Paris. The murder leads them to a trail of clues hidden in the works of Leonardo da Vinci, revealing a religious mystery protected by a secret society for two thousand years. The mystery involves a conspiracy within the Catholic Church and threatens to overturn the foundations of Christianity.

The book is a sprawling narrative that intertwines two timelines: the first during World War II, focusing on the efforts of cryptographers and mathematicians working to break Axis codes, and the second in the late 20th century, following a group of entrepreneurs and hackers establishing a data haven in Southeast Asia. The novel explores themes of cryptography, mathematics, and the history of computing, weaving together real historical figures with fictional characters. As the plot unfolds across different continents and eras, it delves into the impact of information technology on society and the perpetual conflict between governments and individuals over the control of information and privacy.

In "Old House of Fear," the protagonist, an American envoy, travels to a remote Scottish island to negotiate the purchase of an old mansion. Upon arrival, he encounters an atmosphere of mystery and terror, fueled by local superstitions and the eerie presence of the mansion itself. As he delves deeper, he faces a series of supernatural occurrences and a sinister conspiracy, challenging his skepticism and forcing him to confront his deepest fears. The novel blends elements of Gothic horror with a modern psychological thriller, creating a gripping and suspenseful narrative.