A suspense film that can run two hours without the audience getting restless must be pretty good. Alfred Hitchcock’s The Man Who Knew Too Much, screenplayed by John Michael Hayes from a story by Charles Bennett and D.B. Wyndham-Lewis, meets this test. 

Hitchcock fans have reached the “show-me” point where they practically challenge him to bring forth enough new cinema inventiveness to hold them on the edge of their seats all through the show, and in his latest Paramount production the old master of suspense and mystery proves he has plenty of tricks left in his bag. 

His surprise scene de resistance this time is an elaborate sequence in which the London Symphony Orchestra and Covent Garden Chorus, performing in Albert Hall with Bernard Herrmann as conductor, serve as musical propulsion sans dialogue to carry the action to a smashing climax. This highspot is ingeniously signaled in advance, as a suspense plant, by having a member of the orchestra symbolically poised to clash the cymbals as the musical crescendo strikes its top note — which can drown out the fatal pistol shot intended to liquidate a visiting ambassador.

Although Hitchcock dwells rather long and lovingly on some portions of the material, his facile directorial paint-brush, plus the intriguing backgrounds and interesting characters, combine to hold audience interest keyed up at all times. It’s like a long novel that could be tightened, yet many would prefer it as it is. 

Jimmy Stewart, Doris Day and muppet Christopher Olsen constitute an American family group on a tourist trip to North Africa. Enroute to Marrakech by bus, they strike up an acquaintance with an affable and mysterious young Frenchman, Daniel Gelin, who is being trailed because he’s involved in some international intrigue and knows about the impending assassination of the ambassador in London. Just before dying from a stab in the back inflicted by his enemies, Gelin imparts the information about the murder plot to Stewart.

In order to keep the latter from interfering, the political plotters kidnap his little boy and hold him as hostage. Stewart and Doris make a getaway and head for London, where their son also has been spirited and then begins the nervewracking routine of following up clues, running into dead-ends, being slapped with surprises, disappointments and new threats and dangers, until they hit the right track and arrive on the Albert Hall concert scene in time to prevent the assassination. It’s a tumultuous and lavish windup with a dramatic wallop. 

Stewart gives one of his best performances, easy going at the start, then working up to an action tempo as the plot thickens. Miss Day functions very nicely opposite him, proving she does not need a predominantly singing voice in order to click with an audience — although the story does call for her to do a couple of singing stints. Young Olsen is good as the kidnapped boy, while Brenda de Banzie and Bernard Miles perform smoothly as a married couple who carry out the kidnapping after having ingratiated themselves with the family.