Unable to tell his girlfriend, Cathy Muller (BRIDGET MOYNAHAN), of his real job, Jack suddenly finds himself at the side of CIA director Bill Cabot (MORGAN FREEMAN) and traveling to meet Nemerov and his ex-KGB advisor, Anatoli Grushkov (MICHAEL BYRNE), who don't think unrest in Russia is of any concern to the U.S.

After visiting a nuclear research facility and noting that three of the scientists are missing, however, the agents' suspicions are aroused. Accordingly, Cabot gets in touch with government operative John Clark (LIEV SCHREIBER) to find out what happened to them and what they might be up to.

Little do they know that they're working for Richard Dressler (ALAN BATES) a wealthy European industrialist and neo-Fascist leader who's acquired a long missing nuclear warhead from South African arms dealer Olson (COLM FEORE). Convinced that he can sway people over to his ideology after anonymously starting WWIII by pitting the U.S. and Russia against each other, Dressler sets his plan into motion.

As the various agents continue to do their work, catalytic global events begin to occur that lead the superpowers ever close to all out nuclear strikes on each other. With U.S. President Fowler (JAMES CROMWELL) trying to figure out what to do, and working with the advice of Defense Secretary Becker (PHILIP BAKER HALL), Secretary of State Owens (RON RIFKIN) and National Security Advisor Revel (BRUCE McGILL), Jack races to find out the truth and prevent nuclear Armageddon from occurring.

The Jack Ryan films based on author Tom Clancy's best-selling novels already went through such a switch when Harrison Ford appeared in "Patriot Games" and "Clear and Present Danger" after Alec Baldwin initiated the character in "The Hunt For Red October."

That wasn't too big of a deal since Baldwin didn't have the time to make the role his, and most viewers just accepted that Ryan had aged and moved up through the CIA over the passage of time. Now, however, and for reasons that aren't really crystal clear or that important, Ford has opted not to reprise the role. Stepping into his shoes is Ben Affleck who puts a fresh spin on the character in the filmed adaptation of Clancy's 1991 novel, "The Sum of All Fears."

At this point, you may be wondering why the lengthy dissertation if such changes are the norm. Well, the big deal is that not only is the Ryan character now suddenly and noticeably younger in appearance, but he's also suddenly that much younger in character, lower in status at the agency, and his wife is back to being his girlfriend and their kids are persona non grata.

That wouldn't be that big of an issue had the story been a prequel taking place before or around the time of "Red October," but the setting is 2002 and there's no explanation of what's occurred. Did Ryan discover a secret CIA time machine, travel into the past and then send his younger version into the future? The answer, of course, is that Paramount wants to start the franchise anew, but the massive switcheroo is apt to distract anyone familiar with the Ford versions, at least for part of this movie.

All of that said and aside, the question remains about whether this latest installment works as a standalone piece of entertainment. The answer is that it does, but only as long as one is able to accept and/or ignore any number of faults that run through it, not to mention part of the plot closely resembling that which occurred in the 1977 thriller, "Black Sunday."

The film certainly starts off fine with all of the standard and to be expected Clancy flourishes including political unrest, global happenings and the inner workings of the U.S. government at its most secret levels. Many will also be reminded of 1997's "The Peacemaker," an international thriller that also dealt with missing nuclear warheads.

Yet, with the Ryan character reduced back down to an entry level analyst, the fun is in watching him react to the escalating events and interacting with the more veteran and seasoned officials. The pacing is decent, the dialogue and humor are just right for the genre, and Ben Affleck ("Changing Lanes," "Pearl Harbor") and Morgan Freeman ("High Crimes," "The Shawshank Redemption") range from decent to good in their respective lead roles.

Then, an event occurs that - in the wake of Sept. 11th and concerns about future terrorist activities - is not only shocking in terms of the plot, but also more than a bit unsettling and possibly too close to home for some viewers. It's not really a fault of the film - as it was shot before Fall 2001 - but the result, much like the character continuity issue with the previous films, is apt to remove the viewer, at least momentarily, from the proceedings.

After that, the film unfortunately begins to unravel. While the notion of the U.S. and Russia heading toward potential nuclear Armageddon is effective in terms of suspense, the way it plays out, along with the details behind that and the aftermath of the big, shocking event somewhat undermine the effort.

Director Phil Alden Robinson ("Field of Dreams," "Sneakers"), who works from the screenplay adaptation penned by screenwriters Paul Attanasio ("Quiz Show," "Donnie Brasco") and Daniel Pyne ("Any Given Sunday," "Pacific Heights"), has to cram a lot of material and developments into the third act, and the result feels a bit truncated and rushed. It's almost as if the story needed a mini-series approach to work best.

That's not as bad as the catalytic elements behind the evil doings. Now stemming from the work of neo-Fascists rather than Arabs as occurred in the novel, the plan, while possible in concept, seems rather implausible and/or unlikely as presented here.

In turn, that's not nearly as hard to accept as the many elements that then follow the big, shocking event. Suffice it to say, and without going into any details, many of the moments and developments might be able to ratchet up the suspense for non-discerning viewers, but others will easily spot and be distracted by all of the rampant implausibility (including, but not limited to Ryan's character essentially saving the world) that ensues.

It's during all of that where Affleck's character and performance feel the most contrived. Before then, he's mostly okay in the role, and has some decent moments playing off Bridget Moynahan ("Serendipity," "Coyote Ugly") as his girlfriend. Freeman, as usual, is superb in his role, while the likes of James Cromwell ("The Green Mile," "Babe"), Philip Baker Hall ("Rules of Engagement," "Magnolia") and Ron Rifkin ("The Majestic," "L.A. Confidential") are all solid in embodying their respective government-based characters.

Liev Schreiber ("Kate and Leopold," the "Scream" films) is good in his brief role as a covert operative, but it's Ciaran Hinds ("Oscar and Lucinda," "Excalibur") and Michael Byrne ("The Musketeer," "Tomorrow Never Dies") who stand out playing the Russian president and his ex-KGB advisor.

Decent for a while, but nothing spectacular, the film briefly peaks during the unexpected and shocking development, but then begins to fall apart and become less believable as things progress from there until the end. Even so, if you can manage to turn off your brain or at least the more critical and analytical part of it, this isn't a half bad political thriller. "The Sum of All Fears" rates as a 6 out of 10.