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 the second installment in a historical fiction series that weaves together romance, science fiction, and adventure. It continues the story of a 20th-century Englishwoman who has time-traveled to 18th-century Scotland and fallen in love with a dashing Highland warrior. As the Jacobite rebellion leads to the fateful Battle of Culloden, the couple faces the threat of being torn apart by the tumultuous events of history. Interwoven with their past is the present-day narrative of their daughter, who discovers her parents' remarkable story and the truth of her own origins. The novel explores themes of love, loyalty, and the impact of the past on the present.

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.