Although Alfred Hitchcock made several better films than this, including the 1956 remake, The Man Who Knew Too Much is a milestone film for the rotund master of suspense. It was the first film that got him noticed outside the United Kingdom, it led to bigger budgets for Hithcock to work with in British film industry and eventually to his departure for America.
Leslie Banks and Edna Best, Mr.and Mrs. upper class British couple on holiday in Switzerland with their adolescent daughter Neva Pilbeam. A Frenchman they befriend, Pierre Fresnay, is killed right in front of them on a dance floor and he whispers something to Banks about a planned assassination in London to occur shortly. The spies suspect what the dying Fresnay has said to Banks and grab Pilbeam to insure the silence of her parents.
The rest of this short (75 minute) feature is Banks and Best trying to both foil the assassination and get their daughter back. At the climax Best's skill at skeet shooting becomes a critical factor in the final confrontation with the villains.
Peter Lorre made his English language debut in The Man Who Knew Too Much and was very effective with the limited dialog he had. I've often wondered why Hitchcock never used Lorre more in some of his later features.
Although the 1956 version has far better production values, this version still holds up quite well and is worth a look.