The climax of "National Treasure: Book of Secrets" comes when the principal cast races back and forth across a teetering, decrepit mechanical platform that threatens to come apart beneath their feet, much as the script has been doing the previous two hours.

This sequel to the phenomenally successful 2004 history-and-stunts adventure returns us to a world of convoluted conspiracies, legendary troves of gold and patchy plotting, barely held together by the frenetic overacting of Nicolas Cage and company. If the film took itself at all seriously, it would be intolerable, but any movie that casts comic book fan Cage as a brilliant historian is goofing with us, so the best path is to shrug and enjoy the pretty locales. Besides, it's refreshing to see an action movie whose hero is a brainiac pacifist.

As before, Cage is out to clear his family name, besmirched by Ed Harris, who presents evidence that links Cage's great-granddad to the Lincoln assassination. Cage faces family difficulties in the present, as well. He has left girlfriend Diane Kruger because of her overuse of the word "so," and moved in with his long-divorced father, Jon Voight.

Close examination of John Wilkes Booth's diary points to the existence of a Mayan treasure, but Cage can't decipher the hieroglyphics without the help of his mother, sending dad into comic paroxysms of opposition. As Cage follows a bread-crumb trail of clues from Paris to London to Mount Rushmore, Harris shows up from time to time for a Jerry Bruckheimer Car Chase Sequence. The film is baffling -- the scheme that links the conspirators throughout three centuries would flummox the Illuminati -- but as a sort of vacation scrapbook of the lovely places where the cast spent last summer, it's pleasant enough.

They do seem to be having fun. Cage goes mental in a scene at Buckingham Palace; the ruses they employ to get into high-security areas are Scooby-Doo dumb (carry a vase of flowers and no one will question you), and Justin Bartha injects the story with happy juice as Cage's underappreciated techie sidekick. As an added treat, the Disney company opens the feature with a new Goofy cartoon about the clumsy Everydog's misadventures installing his new home theater system. The delirious short subject alone is worth the price of admission; consider the movie a cheesy side dish.

Colin Covert • 612-673-7186