'ffolkes' is an admirably crisp, incisive counter-terrorist thriller, the most proficient and entertaining movie of its kind since Richard Lester's "Juggernaut." Once again the dilemma is extortion on the high seas. Posing as journalists, six hijackers under the command of Anthony Perkins, playing a smug psychopath called Lew Kramer, seize control of a Norwegian supply ship, the Esther, en route to neighboring oil rigs, Ruth and Jennifer, in the North Sea.

Under cover of the normal transfer of supplies, two members of the gang submerge and affix electronically controlled limpet mines to the base of the rigs. After boobytrapping the ship as well, Kramer announces his demands: 25 millions pounds within 24 hours. Having a little joke, he adds that the loot must be divided among five different currencies, since "the money market is so unstable these days."

Thanks to the foresight of an insurance company, presumably Lloyd's, Kramer isn't sitting quite as pretty as he imagines. Weeks earlier an eccentric former naval officer named Rufus Excalibur ffolkes, the founder of a team of trouble-shooting free-lance frogmen called ffolkes' ffusiliers, had accepted a commission to devise contingency plans against just such a bold act of piracy. While the Royal Navy is caught short by Kramer's gang, the ffolkes team is ready for action on short notice.

Being something of a professional smarty pants, ffolkes is also keen for the challenge. Although Jack Davies' screenplay, derived form his own novel "Esther, Ruth and Jennifer," is streamlined for suspenseful action, and there's rarely a wasted or superfluous scene in the film, a fair amount of astute characterization is suggested on the wing and off the cuff.

One of the more effective points, both psychologically and melodramatically, is the suggestion that Kramer and ffolkes have egotistic and intellectual affinities. It's like the opposition of Professor Moriarty and Sherlock Holmes. One man functions as a ruthless criminal predator while the other remains a crankish protector of society, but in certain respects they behave and think alike.

One can understand why Roger Moore might have leaped at the opportunity to play ffolkes. The character's eccentricities are so plentiful, beginning with the spelling of his last name, that Moore probably felt liberated from the rigidities of the James Bond role while embodying a similar kind of heroic gent. In addition to his formidable air of superiority, ffolkes is distinguished by a George V beard, an Edwardian wardrobe, a fondness for cats and straight shots of vintage whiskey, a resort to needlework when he needs to think and a disdain for the opposite sex.

The misogyny is an amusing setup. While ffolkes never quite recants, circumstances oblige him to express grudging admiration for the guts demonstrated by Faith Brook (the daughter of the late Clive Brook) as the prime minister herself, who consents to let ffolkes try his stuff rather than knuckle under to blackmail, and by Lea Brodie as the Esther's intrepid cook, who fails in a daring attempt to poison Kramer but is strategically placed to save the climactic night infiltration mission of the ffusiliers from ending disastrously.

Davis has even been playful enough to invent a witty "explanation" for ffolkes' hostility to women. During one conversation with an exasperated reprsentative of the government, ffolkes blurts out a family history so outrageously prejudicial that is may be accepted as the humorous key to his own prejudices.

The supporting cast is also notable for excellent work by James Mason as a phlegmatic but stalwart admiral, Jeremy Clyde (once of Chad and Jeremy) as the Lord Privy Seal and Michael Parks as Perkins' principal henchman, a myopic electronics wizard who gets a suggestive sort of excitement out of his boss' intimidating behavior. Though never remarkably inventive, Andrew V. McLaglen's direction is alert and trim.

Finally, cat lovers should be advised that Davies has dreamed up a charming fadeout that will prove especially gratifying to them.