Little Phillipe (Bobby Henrey), the ambassador's son has free rein of the embassy while his father is away. His best friend the butler Baines (Ralph Richardson) and the nasty, gripy, strict, Mrs. Baines (Sonia Dresdel) look after him.
One day he finds that Baines sneaks out to visit his "niece" Julie (Mich'le Morgan) who just happens to be an embassy secretary. It becomes a secret. But you know who weasels it out of the boy and replaces it with her secret.
A confrontation peruses and some one is found dead. The boy is pretty sure who did it and decides that is a secret.
The boy decided the Mr. Baines is bad but is told:
Baines "We should be very careful Phil; because we make one another",
Phillipe "I thought god made us?",
Baines "Trouble is we take a hand in the game."
Phillipe now knows the danger in secrets and the departing detective asks "Do you want to know a secret?"