The murder is part of a plot on the part of some members of the Catholic Church to cover up a fact that would change all Christian belief: That Jesus was married to Mary Magdalene; that she was pregnant by him when he was crucified, and that she fled to France and had his child. Langdon and Sophie end up chasing after the Grail (which would actually be Mary Magdalene's tomb) assumedly in order to keep the bad guys from covering up the fact that it, and the offspring existed.

From there, the movie plunges into the ho-hum thriller situation wherein an innocent man and a female companion try to discover the real criminals, while running from the police. They manage to escape from Paris, and Langdon just happens to know a nearby rich history scholar (Ian McKellen) with a convenient slide show in his den that explains all about the Grail. And then when the mad albino monk (Paul Bettany), who's killing everybody, shows up before the cops do, the rich friend also happens to have a jet plane nearby that can take our heroes wherever they want to go.

The action is nonexistent. Basically, the whole formula comes down to a long-winded discussion about art, religion and one Very Big Secret, with the mandatory chase scene involving the world's most fumbling policemen. Sophie offers no romantic interest, sticking around mostly to help forward the plot. The only actor who thrives at all under these conditions is McKellen, who brings wit as Langdon’s rich pal. Rather than being intriguingly provocative, the whole thing comes off as just plodding, tedious and deathly dull.