Montreal Heralds Lively Movies

ONE benefit of visiting an international conclave like the Montreal World Film Festival is that it provides temporary relief from the debates over ''Forrest Gump'' and ''Natural Born Killers'' that have audiences all a-twitter back home.

Debates, disagreements, and disgruntlements happen here, too, but at least there's a fresh batch of movies for them to swirl around. Several of the festival's most heralded offerings, moreover - including a particularly prominent group of American and British productions - have been received by critics with a surprising degree of unanimity, either pro or con.

A small but absorbing American picture called What Happened Was has gathered as much praise as anything I've seen here, and deservedly so. It originated as a stage play written by and starring Tom Noonan, whose performances in movies ranging from ''Mystery Train'' to ''Last Action Hero'' have established him as a versatile character actor.

Noonan's film version of ''What Happened Was'' retains the look and feel of a theatrical production, focusing on only two characters - a secretary and a paralegal who work for a Manhattan law firm - as they eat a modest dinner, have a friendly but awkward conversation, and work their way up to a little flirting that neither seems comfortable with.

On paper, this sounds like a sure-fire candidate for most tedious movie of the season: a full-length drama about two small-timers whose biggest achievement is thinking up some limp remark to keep the conversation from falling totally apart before it's time to say goodbye. What makes it a riveting experience is its combination of sensitive screenwriting - charged with clear understanding of the characters and strong compassion for their lonely lives - and stunningly good performances by Karen Sillas as the hostess and Noonan as her gentleman caller.

Also striking is the film's use of expressive camera work to bring out subtle dynamics of the ever-shifting relationship it portrays. Noonan is equally inventive as an actor, screenwriter, and director.

Another offering that pleased most Montreal observers is Princess Caraboo, an American and British coproduction. Mingling a suspenseful story with a frolicsome mood and occasional dark undercurrents, it's based on the true story of a mysterious young woman who appeared in an English town during the early 19th century, sparking great interest with her exotic manners and unknown history.

There's much to enjoy in filmmaker Michael Austin's account of her unexplained arrival, her growing fame in British society, and her immersion in a controversy that puts her in deadly danger. Still, the movie's pleasure comes less from its plot than from its crisp performances by Phoebe Cates as the so-called princess, Jim Broadbent and Wendy Hughes as upper-crust folks who take her in, John Lithgow as a scholar who studies her, Kevin Kline as a servant who suspects her, and Stephen Rea - fresh from ''The Crying Game,'' another keep-'em-guessing conversation piece - as a journalist who becomes a key player in her little game.

A movie given mixed notices by most critics at Montreal is The Browning Version, adapted by Ronald Harwood from Terence Rattigan's respected stage drama. As in the original play and the first film version with Michael Redgrave, the protagonist is an aging English schoolteacher who's becoming painfully aware of the emptiness and loneliness he's accumulated during a lifetime of rigid pedantry.

Just about everyone who's seen the new ''Browning Version'' agrees that Albert Finney, one of Britain's most brilliant actors, is at the top of his form in a demanding and sometimes daunting role. Greta Scacchi and Matthew Modine are also strong as the main character's unfaithful wife and her secret lover. Less impressive is Mike Figgis's filmmaking, which is visually unimaginative and relies far too much on Mark Isham's overbearing music.

Very low in most critical estimations here is Mesmer, based on the life and career of the 18th-century physician who studied and exploited the power of suggestion while having only the dimmest understanding of what it was. At some points the movie promises to become a daringly satirical comedy, while at other points it sinks into goopy romance or half-baked historical drama. Its indecisiveness and overall lack of distinction come as a surprise, given the solidly gifted group who made the movie - director R oger Spottiswoode, screenwriter Dennis Potter in one of the last projects he completed before his recent death, composer Michael Nyman, and an attractive cast including Alan Rickman and Amanda Ooms.

It's hard to say just where the picture goes wrong, since it rarely finds its footing for more than a scene or two at a time. Perhaps too many talents tried to stir it in too many directions at once. The result is sadly unpalatable.

* ''What Happened Was'' contains adult subject matter in its dialogue. ''Princess Caraboo'' contains moments of sex and vulgar language. ''The Browning Version'' has four-letter words and a sex scene. ''Mesmer'' deals at times with sexuality and violence.