The Man Who Knew Too Much (1956) - Plot Summary Poster


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  • An American physician and his wife take matters into their own hands after assassins planning to execute a foreign Prime Minister kidnap their son.

  • While in London, for a medical convention, Dr Ben McKenna, his wife, Jo, a former singer, and their teenage son, Hank decide to take a quick trip to Marrakesh. Whilst there, hanks kidnapped by a British couple. A man, who the McKenna's had met the same day, is stabbed, in front of them, but before he dies, he tells Ben there's a plan to assassinate on a politician. Fearing for his son's safety, the McKenna's don't tell this to the police. As the he clock grows ever closer - to the l both the speed time of the assassination, and to dealt find Hank, the tension ratches up.

  • Dr. Ben McKenna, his wife Jo and their son Hank are on a touring vacation of Africa when they meet the mysterious Louis Bernard on a bus. The next day, Bernard is murdered in the local marketplace, but before he dies, he manages to reveal details of an assassination about to take place in London. Fearing that their plot will be revealed, the assassins kidnap Hank in order to keep the McKenna's silent. Ben and Jo go to London and take matters into their own hands.

  • The title character is American doctor Ben McKenna. On vacation in Morocco with his wife Jo and his eight-year-old son Hank, he inadvertently witnesses a murder in a market and becomes privy to a plot of political assassination. This being masterminded by the Draytons, an English couple they have met in a restaurant, and is due to take place in London in a few days' time. In order to prevent McKenna from going to the police, the couple kidnap Hank. Ben is warned not to tell the police what he knows. Hank's life depends on his silence.


The synopsis below may give away important plot points.


  • While on an extended European vacation following a medical conference in Paris, American physician Ben McKenna (James Stewart) and his family, whom make up of his wife Jo (Doris Day) and their 11-year-old son Hank (Christopher Olsen) are traveling on a bus in French Morocco when Hank accidentally pulls the veil off a Muslim woman. An international incident is avoided when Louis Bernard (Daniel Gelin), a Frenchman, intercedes on the McKennas' behalf. While Ben is happy to tell Louis all about his family and their planned excursions in Marrakech, his wife Jo is suspicious of the Frenchman's constant questioning.

    That night, Louis meets the McKennas in their hotel room for dinner, but suddenly cancels their supper plans when Rien (Reggie Nalder), a hired assassin, appears at the McKennas' door. Later, at an Arab restaurant, Ben and Jo meet a British couple, the Draytons (Bernard Miles and Brenda de Banzie), who claim to be fans of Jo, who was a well-known singer prior to her marriage to Ben.

    The next morning, the McKennas and Draytons meet at the local marketplace. The usual frivolity of the market crowd is broken when a man being chased by the police collapses in Ben's arms, having been fatally stabbed in the back. It is Louis, disguised as an Arab, who, with his dying breaths, tells the physician that there is a plot to assassinate an unnamed statesman in London. With his final breath, Louis tells Ben to get to London to contact the authorities to tell them to "try Ambrose Chapel".

    While the McKennas are taken to the police station for questioning, Mrs. Drayton agrees to care for Hank in their absence. A police detective reveals that Louis Bernard was a spy working for the French government. Just then, Ben receives a telephone call from a mysterious man who informs him that Hank has been kidnapped and threatens to harm him unless the McKennas say nothing to the police about Bernard's last words. After arriving back at the hotel, Ben learns that Mrs. Drayton never arrived back with Hank, and that her husband, Mr. Drayton checked out a half-hour ago.

    After giving the high-strung Jo a sedative, Ben informs his wife that their only son has been abducted. Aware that the Draytons left Marrakech on a private plane, Ben and Jo decide to go to London and search for Hank there. Greeted at the airport by both Jo's fans and the police, the McKennas are interviewed by Inspector Buchanan (Ralph Truman) of Scotland Yard, who tells them that he is well aware of the reason why their son was kidnapped. Despite his wife's pleas, Ben refuses to tell the inspector what Louis said to him, claiming that the British secret agent had spoken to him in French. Jo then receives a phone call from Mrs. Drayton, who allows the McKennas to briefly speak to Hank.

    Checking into a London hotel, the McKennas attempt to call Ambrose Chapel, the name Louis told Ben, but they are interrupted by the arrival of Jo's old acquaintances: Val and Helen Parnell (Alan Mowbray and Alix Talton), Jan Peterson (Hillary Brooke) and Cindy Fontaine (Carolyn Jones). While Jo stays behind with her friends, Ben sneaks out through the hotel's service entrance to meet Chapel. At the Ambrose taxidermy shop, Ben is slow to realize that neither Ambrose Sr. nor Ambrose Jr. is involved in his son's kidnapping, and is forced to make a quick escape before the police arrive.

    Meanwhile, at the hotel, Jo realizes that "Ambrose Chapel" is a place, not a person, and she is soon met there by Ben. Inside the church, Hank is being held captive by the Draytons, whom are the leaders of an international anarchist group. An assistant named Edna is assigned to watch over Hank. Also there is Rien, who is being instructed by the Draytons as to the exact moment during an Albert Hall concert that he is to commit the assassination: at a climactic cymbal crash in the performance of a cantata.

    The McKennas enter the chapel just as the service, administered by Mr. Drayton, is about to begin. While Ben stays inside, Jo leaves to call the police, so the Draytons cut short the service. Hearing his son's voice, Ben rushes to Hank's aid, only to be knocked unconscious by one of Draytons' henchmen. By the time the police arrive at the chapel, the Draytons have made their escape with Hank. Refusing to enter the locked church without a search warrant, the police leave, so Jo calls the police station, begging for help. She asks to speak to Buchanan, but is told that he is at an important diplomatic function at a concert at Albert Hall. When the policeman refuses to contact Buchanan, she heads off alone to Albert Hall to find him. When Rien sees her there, the assassin reminds Jo that Hank's safety depends on her silence.

    Meanwhile, Ben escapes the locked chapel by climbing the church bell's rope and also makes his way to the concert. Realizing that Rien is about to shoot a visiting foreign prime minister, Jo screams, causing the startled assassin to merely wound the dignitary in the arm. Ben then jumps Rien, and in his attempt to escape, the assassin falls from the balcony to his death.

    At the embassy, the Draytons hide out there where are informed by the ambassador (Mogens Wieth) (who hired them for the assassination job) that their assassination attempt on the prime minister has failed. Despite Mrs. Drayton's objection, the ambassador then orders her husband to kill Hank. With the police unable to go into the embassy due to diplomatic immunity, the McKennas enter alone, as the invited guest of the grateful prime minister. Jo is asked to perform for the guests, and her singing voice is soon recognized by Hank. Under Mrs. Drayton's instruction, the young boy whistles along with her singing, guiding Ben to the room in which his son is being held. Mr. Drayton then appears, but rather than killing them, he decides to use Ben and Hank as human shields during his escape from the embassy. As they make their way down the grand staircase, Ben pushes Drayton, and the spy is killed when he falls on his own gun.

    In the final scene, the reunited McKennas then head back to their hotel room, where Jo's friends have been waiting the entire time.

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