In my opinion "The Man Who Knew Too Much" (1956) is Doris Day's best thriller. Costarring the always wonderful James Stewart, this movie is an Alfred Hitchcock remake of a film by the same name that he made in 1934. Day plays Jo McKenna, wife of Dr. Ben McKenna (Stewart). The couple are vacationing with their son Hank (Christopher Olsen) in Morocco. On a bus trip, they make the acquaintance of a friendly Frenchman named Louis Bernard (Daniel Gélin). Although Jo finds him a bit suspicious, they agree to go out to dinner with him that night. However, Bernard suddenly excuses himself at the last minute. Out on their own, Ben and Jo meet an English couple named Lucy and Edward Drayton (Brenda de Banzie and Bernard Miles) at the restaurant and also see their French friend, who sits with another group and does not acknowledge them.
Touring the Marrakesh marketplace the next day with the Draytons, the McKenna family sees a man being chased and then stabbed. The dying victim turns out to be the Frenchman Bernard, who approaches Ben and whispers to him that an important foreign statesman will be murdered in London, and that he must inform the authorities about an "Ambrose Chapel". The McKennas are asked by the authorities to accompany them to the police station, and Mrs. Drayton offers to take Hank back to the hotel with her. While at the station, the McKennas learn that Louis Bernard was a French intelligence agent on assignment in Morocco. Then Ben receives a mysterious phone call informing him that Hank has been kidnapped and that he should not reveal Bernard's last words to the police if he wants to see his son alive again.
The McKennas travel hurriedly to London and are met by a Scotland Yard inspector who confirms that Bernard was a spy and urges the McKennas to contact him should they hear from the kidnappers. The McKennas decide instead to try to find Ambrose Chapel on their own. They incorrectly assume that this is the name of a man, but after following an unsuccessful lead, they realize that Ambrose Chapel is the name of a building where the kidnappers have based their operation. Unfortunately, the kidnappers escape with Hank before Ben and Jo can rescue him. They do, however, manage to foil the assassination plot, and eventually are able to recover Hank as well in a daring move at a foreign embassy.
Hitchcock excels at films about ordinary people caught up in extraordinary circumstances, and this one is no exception. Stewart and Day are perfect as the all-American couple, and as Day's character is a retired popular singer, she even gets to sing in the movie. This is the only Hitchcock movie where a character has a singing role, and the song was commissioned especially for Day. That song was "Que Sera, Sera" ("Whatever Will Be, Will Be"), which became a popular hit and won a 1956 Acadamy Award for Best Song. If you want to watch a truly enjoyable film with an exceptional performance by Doris Day (and James Stewart!), then this is the movie to see.
Interesting Facts: Doris Day had two songs nominated for an Academy Award in 1956 -- the other was the title song for the movie "Julie". Also, Day's dismay at the poor treatment of animals in Morocco led to her insisting on their better treatment during filming, and resulted in her lifelong commitment to animal welfare.
"Que Sera, Sera" became Doris Day's signature song. You can watch her singing this song in the movie on YouTube: