Angels & Demons, about an ancient secret society that is trying to disrupt the Vatican, is based on the book that Dan Brown wrote before he struck gold with The Da Vinci Code.

It stars Tom Hanks, back again as Harvard University “religious symbologist” Robert Langdon, this time running around Rome looking to rescue four kidnapped cardinals and a canister containing a blob of antimatter before it explodes.

Antimatter? Hatched at the nuclear supercollider in Switzerland and then stolen, it’s the thing that Langdon, joined by a pretty scientist from the Swiss facility, Swiss Guards, and the Rome police race around the city trying to find, using clues that bring them to ancient churches, tombs and underground crypts. If it goes off at midnight, it will turn Vatican City and a good chunk of Rome into a flash of light and only a memory.

Despite a title that promises something supernatural, Angels & Demons is really a time-is-running-out chase movie — National Treasure with more complex clues, some of which are in Latin.

Although the plot’s bottom line could undermine the Roman Catholic Church, the film doesn’t have the mix of mysticism or the goal of turning around the basic tenets of Scripture that made The Da Vinci Code and its movie version runaway international hits. Hanks, an everyday-kind-of-guy actor who again seems out of his element in what should be a frantic thriller, director Ron Howard and screenwriter Akiva Goldsman are back again (this time with cowriter David Koepp). Howard and Goldsman turned Brown’s page-turner Da Vinci Code into a ho-hum movie. This time they get to play with heightened special effects, yet the end result is much the same.

Allegedly the canister containing the glowing bit of antimatter has been stolen by members of the Illuminati, an ancient society of scientists and progressive thinkers who were hounded by the Vatican back in Galileo’s day. Their theft of the antimatter is seen as a way of getting back at the church. Hidden in Rome, the battery that’s keeping the antimatter contained is wearing down. Once it expires, ba-boom!

Meanwhile, four of the cardinals meeting at the Vatican to elect a new pope have been kidnapped. There’s a threat to kill one of them each hour, leading up to the midnight deadline when the anti-matter is predicted to go off.

Despite the headaches Langdon caused the church by his deciphering of the Da Vinci Code, the Vatican calls on him again, whisking him to Rome to use his expertise. He’s advised by the Pope’s chief assistant, the camerlengo, a self-assured young Irishman named Patrick McKenna (Ewan McGregor) who knows all the Vatican secrets. Langdon is joined on his hunt by collider scientist Vittoria Vetra (Ayelet Zurer) the way he was joined by Audrey Tautou in Da Vinci.

What follows sets them on a labyrinthian trail through Rome (the movie is a terrific tour of the city) in search of the antimatter canister and the whereabouts of the cardinals threatened with death. This includes stops in the catacombs, a sealed climate-controlled book repository with precious little air, and the opening of a crypt that contains the body of a Pope. A picture of the antimatter canister is, meanwhile, being tantalizingly broadcast from its hiding place via a TV hookup.

For all the potential excitement, however, the several hours leading up to the deadline plod along as Langdon and the police sift through a series of clues hidden in books, some of which require special permission from the Vatican to open, some of which are in Latin.

Despite the film’s clock-is-ticking element, director Ron Howard never lets the urgency of the situation build momentum. Angels & Demons soon becomes too predictable in the way each clue eventually leads to the whereabouts of a cardinal (each seen as a briefly anonymous figure), in the last seconds before he is to be murdered, with the rescuers usually arriving too late. The assassin (Nikolaj Lie Kass), who has a very large arsenal and phenomenal good luck in carrying out the plot, is similarly anonymous.

Who are the Illuminati that are the brains behind the operation? The script tosses red herrings every which way so just about everyone, except Langdon, looks like a plausible schemer.

When we finally discover the identity of the perpetrator behind all this mayhem in the final reel, in hindsight one realizes that the plotter has created a complex tripwire plan in which unpredictable events must come together like clockwork.

Screenwriters David Koepp (Indiana Jones and the Kingdom of the Crystal Skull, War of the Worlds, Spider-Man) and Goldsman (The Da Vinci Code, A Beautiful Mind) have created thrilling screen moments in the past. But they’re at a loss as to how to make the more preposterous elements of Angels & Demons a little bit believable.

It doesn’t seem possible that nearly everything could keep coming together so smoothly. Nevertheless the plot is designed, with its mix of grisly shock value and the fantastic, to be a crowd pleaser. An explosive moment over Rome is spectacularly staged, but in its final analysis it strikes one as outrageous.

Despite these flights of fancy, however, the film’s ending is satisfying. For some, that may be enough.

**1/2Angels & Demons

Starring: Tom Hanks, Ewan McGregor, Ayelet Zurer, Stellan Skarsgard, Armin Mueller-Stahl.

Rated: PG-13, contains grisly violence.

mjanuson@projo.com