Wait a minute: Knights Templar? Freemasons? Clues to a mystery hidden within a well-known historical artifact? Sounds a lot like Dan Brown’s book “The Da Vinci Code” to me. In fact, National Treasure is a blatant rip-off of the best-selling novel. Only the artifact has been changed. When I read “The Da Vinci Code,” I thought it was a piece of crap – a preposterous potboiler trying to pass itself off as something scholarly and academic. This film doesn’t have the pretension, thank goodness, but it has all the same ridiculous plotting.

Let me back up. Ben Gates is a self-professed “treasure hunter” in a family filled with them. Grandpa (Christopher Plummer) believed in the story and passed it down to Ben’s father (Jon Voight), who did not believe – at least, not after he failed to find any proof. Ben and a colleague, Ian Howe (Sean Bean), come to believe that the search might begin with an ancient ship frozen somewhere in the arctic. They find the ship (fortunately for them, it was only buried beneath four inches of snow) and locate a clue inside. The riddle of the clue, when solved, suggests that the backside of the Declaration of Independence will reveal the treasure’s exact location.

Ben and Ian have a falling out, at which point it becomes clear that Ian is going to attempt to steal the Declaration. Ben notes that the only way to save the document is to steal it first. He gets assistance from the prerequisite goofy sidekick, Riley (Gigli’s Justin Bartha), and the equally requisite blonde hottie, a National Archives employee named Abigail Chase (Diane Kruger). Each nearly impossible clue leads to another nearly impossible clue, until eventually the group finds itself – you guessed it, “Da Vinci” fans – deep beneath a church!

This movie is dumb all over. For starters, the heist of the Declaration is laughably preposterous. The plan Ben hatches wouldn’t be any less believable if it involved a squadron of flying monkeys. Since the Declaration is locked securely, Ben knows he must wait until its keepers take it out of the case to clean it. Although he lives in a rundown dump of an apartment, Ben possesses millions of dollars worth of high-tech equipment intended only to steal things. (All movie thieves have such things, as we also recently learned in After the Sunset). Using this gear, Riley is able to do that old movie standby: intercepting the security camera feed and using a computer to loop tape of an empty hallway so that Ben can walk down the real one undetected. After that, he pretty much just marches into the room and walks off with the Declaration. Security guards, naturally, are nowhere to be found. Is this how well important historical documents are protected? Someone call Michael Moore!

It doesn’t help that the film lifts entire ideas (bad ones) from Dan Brown’s book. If you believe pop culture, those Knights Templar were pretty busy people. They guarded the secret of the Holy Grail, plus they kept hidden the location of our founding fathers’ secret treasure. For all I know, they’ve been hiding Col. Sanders’ secret recipe as well. The idea is intriguing, up to a point. Both Brown and this film take the idea to such illogical extremes, however, that you can’t help but snicker.

Nothing that happens in National Treasure is even remotely possible. Nothing. For that reason, it is often unintentionally hilarious. I couldn’t cure myself of the giggles during the scene in which Ben and Abigail rub lemon juice all over the Declaration of Independence to bring out the invisible ink. I won’t even try to describe Ben Franklin’s 3-D glasses, which are another clue. The ending, set in the church’s subterranean catacombs, is absurd for trying to turn Ben into an Indiana Jones clone. The cliffhanger action scenes don’t gel with all the talk about our founding fathers and the documents that detail the American way of life.

The only saving grace is the likeability of the cast, although I for one would love to see Nicolas Cage abandon Action Guy mode once and for all. He’s too good an actor to keep making bad Jerry Bruckheimer movies. Even so, it’s hard not to watch Cage, and he is supported by some good actors who try their hardest not to flounder amidst the inanity that is this movie.

The premise of National Treasure is simply too hard to swallow. Nevertheless, the film tries to make us swallow it. Big mistake. I cannot believe they made this movie with a straight face. I sure didn’t watch it with one.

( 1/2 out of four)

National Treasure is rated PG for action violence and some scary images. The running time is 2 hours and 10 minutes.