The Sum of All Fears: Starring Ben Affleck, Morgan Freeman, James Cromwell, Bridget Moynahan and Liev Schreiber. Rated M.

Following the untimely death of Russian President Zorkin, a new, little-known replacement is sworn in with some haste. Virtually unknown to the West, new President Alexander Nemerov is a cause for some concern in the top political and intelligence circles in Washington.

A young political analyst/historian, Jack Ryan is called upon to offer expert advice on the man he studied and wrote a university thesis on just two years previously.

Stepping in to breathe oxygen well above his pay group, Jack Ryan seems to have all the wrong answers when asked and seems not to know when his advice, not being sought, should be kept close.

Invited to accompany CIA deputy director William Cabot to Russia, Jack builds a small, but ultimately crucial bond with President Nemerov.

While touring Russia's main nuclear-weapons decommissioning plant - a facility so highly protected during the Cold War that no one ever penetrated its defences, though many died trying - Jack notices that three top scientists rostered for duty are missing.

Although quick with excuses, the Russians are less than convincing in the cover up, letting the suspicious and probing minds of American intelligence lose on a potentially catastrophic mystery.

Dark agent John Clarke is hired to get to the heart of the matter from the grassroots level while Ryan and Cabot ponder the big picture.

When a Chechnyan town of some size is devastate by a barrage of chemical weapons, things get just a bit tense between the superpowers. Nemerov, afraid of looking weak in the eyes of the world or worse, that he has lost control of his military, claims responsibility.

In the mean time, a radical European terrorist group, clever enough not to fight either the Americans or the Russians directly, acquire a missing Israeli nuclear bomb, intent on using it to start a conflict that will see their two perceived enemies destroy each other. Desperately putting all the pieces together, Ryan finally realises that the bomb does in fact exist and is at that very moment somewhere in Baltimore where his own President Fowler is attending a football match. Ryan alerts the president's men with barely enough time to effect an evacuation.

The bomb goes off, and although it is basically a fizzer yielding only a fraction of the two dropped by America on Japan half a century before, it nonetheless causes mass collateral damage and loss of inosent life - striking a blow a the very heart of America.

With intercontinental tensions high and President Fowler barely escaping with his life, both countries step up to the brink of armageddon with alarming speed.

Only one man believes, and is apparently levelheaded enough, to keep a calm head - calm enough to see the truth - and brave enough to deliver it.

The Sum of All Fears (the movie) is set early in Jack Ryan's career - before he really stamps his mark as an agent of substance on the American intelligence fraternity. Early in his personal life too, having just met the future Mrs Cathy Ryan, world-class eye surgeon - and, of course, future FLOTUS.

A minor, and understandable, deviation in the story line, in deference to the current real-life state of the world, sees a group of neo-nazis form the backbone of evil in Jack Ryan's world, replacing the Middle-Eastern fundamentalist Moslems of the book.

But another, less understandable, deviation from the book - of little consequence to movie - is the aforementioned timeframe in Jack Ryan's career and personal life. In the book it is actually Dr Jack Ryan, not Cabot, who is Deputy Director Central Intelligence with the already accomplished Dr Cathy Ryan the strong woman standing firmly behind her man.

I'm a big Tom Clancy fan. I love his books - especially the ones he actually writes himself. So when another episode in the life of Dr Jack Ryan comes to the big screen, you know I will be there in a flash - and expecting big things.

And of course, I wasn't disappointed.

The plot is big - perhaps too big for the two hours three minutes allotted - and the action is even bigger.

As usual, the full might of the US military plays a Hollywood supporting role adding magnificently to the atmosphere of the best-yet screen adaptation of the world's number one fiction writer. Bring on the next one.

Five shamrocks