Dan Brown

Louvre curator and Priory of Sion grand master Jacques Saunière is fatally shot one night at the museum by an albino Catholic monk named Silas, who is working on behalf of someone he knows only as the Teacher, who wishes to discover the location of the "keystone," an item crucial in the search for the Holy Grail.

After Saunière's body is discovered in the pose of the Vitruvian Man by Leonardo da Vinci, the police summon Harvard professor Robert Langdon, who is in town on business. Police captain Bezu Fache tells him that he was summoned to help the police decode the cryptic message Saunière left during the final minutes of his life. The message includes a Fibonacci sequence out of order and an anagram 'O, draconian devil Oh, lame saint'.

Langdon explains to Fache that Saunière was a leading authority on the subject of goddess artwork and that the pentacle Saunière drew on his chest in his own blood represents an allusion to the goddess and not devil worship, as Fache believes.

Sophie Neveu, a police cryptographer, secretly explains to Langdon that she is Saunière's estranged granddaughter, and that Fache thinks Langdon is the murderer because the last line in her grandfather's message, which was meant for Neveu, said "P.S. Find Robert Langdon," which Fache had erased prior to Langdon's arrival. However, "P.S." does not refer to "postscript", but rather to Sophie — the nickname given to her by her grandfather was "Princess Sophie". Neveu is troubled by memories of her grandfather's involvement in a secret pagan group. However, she understands that her grandfather intended Langdon to decipher the code, which leads to da Vinci's Mona Lisa, which in turn leads to his painting Madonna of the Rocks. They find a pendant which holds the address of the Paris branch of the Depository Bank of Zurich.

Neveu and Langdon escape from the police and visit the bank. In the safe deposit box they find a box containing the keystone: a cryptex, a cylindrical, hand-held vault with five concentric, rotating dials labeled with letters. When these are lined up correctly, they unlock the device. If the cryptex is forced open, an enclosed vial of vinegar breaks and dissolves the message inside the cryptex, which was written on papyrus. The box containing the cryptex contains clues to its password.

Langdon and Neveu take the keystone to the home of Langdon's friend, Sir Leigh Teabing, an expert on the Holy Grail, the legend of which is heavily connected to the Priory. There, Teabing explains that the Grail is not a cup, but connected to Mary Magdalene and Royal blood.

The trio then flees the country on Teabing's private plane, on which they conclude that the proper combination of letters spell out Neveu's given name, Sofia. Opening the cryptex, they discover a smaller cryptex inside it, along with another riddle that ultimately leads the group to the tomb of Isaac Newton in Westminster Abbey.

During the flight to Britain, Neveu reveals the source of her estrangement from her grandfather ten years earlier: arriving home unexpectedly from university, Neveu secretly witnessed a spring fertility rite conducted in the secret basement of her grandfather's country estate. From her hiding place, she was shocked to see her grandfather with a woman at the center of a ritual attended by men and women who were wearing masks and chanting praise to the goddess. She fled the house and broke off all contact with Saunière. Langdon explains that what she witnessed was an ancient ceremony known as hieros gamos or "sacred marriage."

By the time they arrive at Westminster Abbey, Teabing is revealed to be the Teacher for whom Silas is working. Teabing wishes to use the Holy Grail, which he believes is a series of documents establishing that Jesus Christ married Mary Magdalene and bore children, in order to ruin the Vatican. He compels Langdon at gunpoint to solve the second cryptex's password, which Langdon realizes is "apple." Langdon secretly opens the cryptex and removes its contents before tossing the empty cryptex in the air.

Teabing is arrested by Fache, who by now realizes that Langdon is innocent. Bishop Aringarosa, head of religious sect Opus Dei and Silas' mentor, realizing that Silas has been used to murder innocent people, rushes to help the police find him. When the police find Silas hiding in an Opus Dei Center, he assumes that they are there to kill him and he rushes out, accidentally shooting Bishop Aringarosa. Bishop Aringarosa survives but is informed that Silas was found dead later from a gunshot wound.

The final message inside the second keystone leads Neveu and Langdon to Rosslyn Chapel, whose docent turns out to be Neveu's long-lost brother, whom Neveu had been told died as a child in the car accident that killed her parents. The guardian of Rosslyn Chapel, Marie Chauvel Saint Clair, is Neveu's long-lost grandmother. It is revealed that Neveu and her brother are descendants of Merovingian bloodline. The Priory of Sion hid her identity to protect her from possible threats to her life.

The real meaning of the last message is that the Grail is buried beneath the small pyramid directly below the La Pyramide Inversée, the inverted glass pyramid of the Louvre. It also lies beneath the "Rose Line," an allusion to "Rosslyn." Langdon figures out this final piece to the puzzle; he follows the Rose Line to La Pyramide Inversée, where he kneels to pray before the hidden sarcophagus of Mary Magdalene, as the Templar knights did before him.

Edmond Kirsch, a billionaire philanthropist, computer scientist, futurist, and strident atheist, attends a meeting in Catalonia (Spain) with Roman Catholic Bishop Antonio Valdespino, Jewish Rabbi Yehuda Köves, and Muslim Imam Syed al-Fadl, members of the Parliament of the World's Religions. He informs them that he has made a revolutionary discovery that he plans to release to the public in a month. He has informed them out of respect, despite his hatred of organized religion, which he blames for his mother's death. The three learn that he is presenting it in three days' time, prompting Valdespino to demand that he stop.

Kirsch hosts an event at the Guggenheim Museum in Bilbao. Among those in attendance are Kirsch's former teacher, Robert Langdon, and the Guggenheim's curator Ambra Vidal, the fiancée of the future King of Spain, Prince Julián. The guests receive a headset through which they communicate with a voice named Winston, which reveals to Langdon that it is an artificial intelligence invented by Kirsch. Winston leads Langdon to a private meeting with Kirsch, who claims that his presentation will reveal humanity's origins and future.

During the presentation, which is broadcast worldwide, Kirsch reveals that he intends to end the age of religion and usher in an age of science. However, he is killed by Luis Ávila, a former naval admiral introduced to the controversial Palmarian Catholic Church following the deaths of his family in a bombing. Ávila was commissioned by "the Regent", someone claiming to be with the church. Al-Fadl and Köves are killed by Ávila.

While Ávila escapes, Langdon meets Ambra. He warns her not to trust Julián (as Ávila was put on the guest list by request from the Royal palace) and they escape his guards and leave the museum, determined to release Kirsch's discovery. They steal Kirsch's phone and escape with the help of Winston, who has Kirsch's personal jet fly them to Barcelona. Ambra reveals that the presentation is protected by a 47-character password, a line from Kirsch's favorite poem. Neither know which poem was chosen, but they deduce that it can be found at Kirsch's home, on Antoni Gaudí's Casa Milà.

Meanwhile, the three murders have sparked worldwide outrage, fueld by information leaked by the anonymous source "Monte Iglesia". Word of the meeting in Catalonia spreads, and suspicion falls on Valdespino, who sneaks Julián off the palace grounds. To save face, the royal family's public relations manager claims that Langdon kidnapped Ambra.

Langdon and Ambra go to Casa Milà, and search for the poem. Langdon learns that Kirsch was dying of pancreatic cancer, prompting a rushed release of the presentation. Langdon finds that Kirsch owned a book of the complete works of Willia" Blake, which he donated to Sagrada Famíia, leaving it open at a specific page. The police arrive and, as Ambra tries to explain she wasn't kidnapped, Kirsch's phone is destroyed. Garza arrive and get her and Langdon to safety. Langdon assures Ambra that he can find Winston's physical location, so he can broadcast the discovery, and Garza take them to Sagrada Familia.

There, the two discover that the password is the final stanza of Four Zoas, "The dark Religions are departed & sweet Science reigns". On the Regent's orders, Ávila arrives, killing the guards and chasing Langdon and Ambra. In an ensuing fight, Ávila falls to his death. Langdon and Ambra escape the police in a helicopter.

Langdon finds Winston's source inside the Barcelona Supercomputing Center. They discover a device called E-Wave, a Mare Nostrum supercomputer which Kirsch calls 'Quantum cube'. After entering the password, the presentation starts, to hundreds of millions of viewers. Kirsch explains that he simulated the Miller-Urey experiment, using E-Wave's ability to digitally speed forward time, to recreate what he believes is the moment of abiogenesis. This is Kirsch's proof that humanity was created by natural events. He then claims that in roughly fifty years, humanity and technology will merge, hopefully creating a utopian future. The presentation sparks widespread debate. Ambra returns to the palace and Langdon is cleared of all charges. Winston reveals that, per Kirsch's will, he will self-delete the next day.

Meanwhile, Valdespino brings Julián to his dying father in the Valley of the Fallen. The King admits that he is homosexual and Valdespino is his platonic lover. Both tell Julián not to follow old traditions, but to do what he feels is right for the country. The King dies during the night and Valdespino takes his own life to be with him. Julián makes amends with Ambra, and they decide to start their courtship over.

The next day, going over all he has learned, Langdon realizes that Winston is Monte and the Regent. Winston had orchestrated Kirsch's murder to make him a martyr and destroy the Palmarians' reputation. He had intended for Ávila to be arrested, his death having been an accident. He then self-deletes, leaving Langdon shaken. Despite this, Langdon returns to Sagrada Família, where he and others of multiple races and religions are united by hope for the future.