Curator of the Louvre in Paris, Jaques Sauniere, has bin killed inside the museum. Harvard symbologist Robert Langdon is brought in to assist the police in their investigation. The dead man has left a lot of symbols on himself as well as on the floor beside him. Langdon is set to decipher these mystic codes. But what he doesn’t know is that he is the police’s prime suspect in the case. A young cryptologist, Sophie Neveu, tells Langdon he is being manipulated, and together they get away from the police. Langdon manages to solve the codes Sauniere left behind, and they indicate that the information they are looking for are hidden in the works of Leonardo Da Vinci.
Meanwhile Sauniere’s murderer, Silas, a monk of Opus Dei, is on his way to collect a keystone that belongs to a secret society; The Priory of Sion.
Behind one of Da Vinci’s paintings Sophie finds a strange key, and then she and Robert escapes from Louvre and start a race in the streets of Paris. Sophie has now revealed to Robert that Sauniere was her grandfather, and that he most likely was a member of a secret brotherhood. Robert connects her grandfather’s secrets to the secret brotherhood called “The Priory of Sion.” They find an address on the key, and not long after they find themselves in the Paris branch of Depository Bank of Zurich.
Silas has now found out that the lead he had gotten from Sauniere and the three “senechaux” was a dead end. His friend and master in the Opus Dei, Bishop Aringarosa, have met with the leaders of the Vatican, and has bin paid twenty million dollars. These he is intending to spend on getting the Holy Grail, so that his church can have power over the Vatican.
The Police are hunting Robert and Sophie, and are now on their way to the Bank, after getting an anonymous tip.
The key Robert and Sophie found unlocks a bank box, but only if you have the right account number. In a genius moment Robert links a coded number Sauniere left beside him, and the ten-digit code they need and they manage to retrieve a mysterious wooden box from the bank box. Inside they find a cryptex, one of Da Vinci’s lesser-known inventions, meant to hold secret information. Robert understands this has something to do with the secret of the Holy Grail, he believes the cryptex is Priory of Sion’s keystone, that shows the way to the Holy Grail.
The bank manager, Andre Vernet, is very worried of the bank’s reputation and when the Police arrive at the bank he refuses to let them in. And then he helps Robert and Sophie escape in one of the bank’s delivery cars.
After a long drive out of Paris, Vernet discovers Robert and Sophie, are wanted for three more murders, and he decides to take the box from them and return to Paris.
In desperation Robert and Sophie knocks out Vernet, and escapes with the car, leaving Vernet behind.
They head for one of Robert’s friends, Sir Leigh Teabing, an expert on the Holy Grail. As it is in the middle of the night it takes some time to get Teabing out of bed, but at last they meet him and start to explain about their situation. Teabing and Robert now give Sophie the true story of the Holy Grail. The chalice is a symbol for a woman, Christ’s woman. Her name was Mary Magdalene, and she bore the child of Jesus. The grail is said to behold Mary Magdalene’s tomb, and many secret documents that prove that Jesus was married to Mary Magdalene.
Silas is now outside Teabing’s residence. The Teacher ordered him to get there and steal the keystone from Langdon and the girl, without hurting anyone.
Aringarosa is very worried about the situation as neither the Teacher or Silas has called him.
Robert studies the wooden box and finds a strange writing below a carved rose in the lid. In that instant Silas attacks, he knocks out Robert, but Teabing gives him a beating with his crutches. The Police now arrive at the residence and the grail seekers, a bound Silas, and Teabing’s butler flees the estate and takes Teabing’s private plane to England.
The local Police try to stop them, but Teabing pulls off an amazing play and fools the Police. Robert has now managed to open the cryptex, just to find another cryptex and a clue on how to open it. Teabing takes them to the place he thinks the answer lays. But they find nothing, and Teabing’s butler, Remy, shows himself as a traitor. He and Silas take the cryptex, and kidnaps Teabing. Robert and Sophie are now on their own, without any clue on how they are going to retrieve the cryptex. They start to search for information about the place where the cryptex’s password is supposed to be hidden.
Aringarosa is now on his way to London.
The Teacher has got rid of Silas, by sending him to an Opus Dei house in London and he has killed Remy, because he had made a mistake that could reveal the Teacher’s identity. But he has trouble with the last password, and leaves Robert and Sophie a message.
They discover that the tomb they look for is Isaac Newton’s. In Westminster Abbey, they find the tomb and a message that tells them to come to a garden if they want to see Teabing alive.
But this is just a trick; the Teacher and Teabing are actually the same person. He threatens Robert and Sophie with a gun, and gives Robert the cryptex so that he can open it. He walks to a window, and facing away from the other two, he manages to open the cryptex and take out it’s content.
Then he threatens to smash the cryptex, which neither of the other two knows has bin emptied. He throws it high up, and Teabing jumps after it. It smashes on the floor, and then the Police arrive and arrest Teabing. Aringarosa and Silas are both hurt after a shooting outside Opus Dei’s house. Silas dies praying for Aringarosa’s life, and the Bishop survives miraculously.
Sophie and Robert are in a church in Scotland, where they think the Holy Grail lies. But they find no Grail, but Sophie finds her Grandmother and brother, whom she believed was dead. They unite and are very happy. Robert needs to get an answer to the mystery about the Holy Grail and travels back to Paris. There he finds the answer, and the clues lead him to where the whole thing started; the Louvre Museum. There he falls to his knees and thinks he hears a woman’s voice.