Less entertaining than flat-out exhausting, this frantic treasure-hunt movie is so determined to hold your attention that it unleashes a hailstorm of breakneck chases, incomprehensible technology, wild leaps of logic and cliff-hangers that would have seemed hackneyed in the days of Polly Pureheart and Snidely Whiplash serials. As an impressionable child, Benjamin Franklin Gates (Nicolas Cage) learned from his grandfather (Christopher Plummer) their family’s unique and thrilling history. Six generations earlier, in 1832, stable boy Thomas Gates (Jason Earles) was entrusted with the cryptic words “The truth lies with Charlotte” by the last surviving signer of the Declaration of Independence. This clue, declares grandpa, is a link in a chain that ends with the fabulous treasure of the Templar Knights, which vanished during the 14th century and later made its way to the New World. Ben’s black-sheep father (Jon Voight) — which in Gates-family parlance means the one who got a real job — believes the clues were a gigantic hoax from the start, conceived as a diversion to confound the redcoats while our Revolutionary forefathers built their new nation. But Ben embraces the family legacy with the fervor of a true believer, which is why we pick him up in a Sno-Cat somewhere in the Arctic Circle, preparing to uncover the frozen wreck of a ship — the long-lost Charlotte. Accompanied by computer geek Riley (Justin Bartha) and their financial backer, shady adventurer Ian Howe (Sean Bean), he finds not treasure, but another clue. It suggests there’s an invisible map on the back of the Declaration of Independence. Ian’s response — that they need to steal the Declaration — marks the dramatic end of their partnership. Naturally, Riley and Ben fail to persuade the proper authorities of Ian’s evil intentions. So they steal the Declaration themselves, kicking off a race against time and Ian’s gang of goons to locate historical artifacts and decipher their arcane mysteries. Apparently conceived as a family-friendly variation on The Da Vinci Code (one blissfully free of disturbing religious implications), the film unfolds like one of those mind-numbing video games that claim to be educational because they incorporate historical trivia into their repetitive “solve clue/acquire object/advance to next level” format. Full of whos that turn out to be whats, whats that prove to be whos, centuries-old devices in mind-bogglingly good working order and academics with the stamina of Olympic-caliber athletes — including improbably bodacious archivist Abigail Chase (Diane Kruger) — it’s a silly, stupendously artificial enterprise.