A book containing a transcription of some historical conversation has someone by the name Fred asking a question:
Fred: "What is the recipe for Orange Julius?" [Whispers.]
George: "No, it is ..."
Does the bracketed [Whispers.] refer to some unknown words spoken following "What is the recipe for Orange Julius?", or does it mean that the phrase "What is the recipe for Orange Julius?" itself was whispered?
If the answer is the latter, would it be clearer to do this:
Fred: [Whispers:] "What is the recipe for Orange Julius?"