The Man Who Knew Too Much (1956)

While attending a medical conference in Paris, an American physician, Dr. Ben McKenna, along with his wife, retired musical theater actress and singer Jo McKenna née Conway, and their adolescent son, Hank McKenna, decide to take a side trip to Marrakesh, French Morocco. On the bus to Marrakesh, they meet a Frenchman, Louis Bernard. The following day at the market, Louis is masquerading as an Arab and approaches Ben with a knife plunged in his back. Before dying, Louis cryptically whispers into Ben's ear that there will be an attempted assassination in London of a statesman. Ben is reluctant to provide any information of this news to the authorities because he learned Hank was kidnapped by a British couple, Edward and Lucy Drayton. The people the Draytons were working for threatened to kill Hank if Ben divulged any information told to him by Louis Bernard. With what little information they have on hand, Ben and Jo head to London to try and thwart the assassination attempt and more importantly find Hank alive and safe. Scotland Yard is aware of some pieces to the puzzle, including the fact that Louis Bernard was a French secret service agent and that there will be an assassination attempt on someone. They will have to work together as they hit a diplomatic roadblock, one that may be overcome with a special Jo Conway song.