“Does she want to see Gatsby?”
“She’s not to know about it. Gatsby doesn’t want her to know. You’re just supposed to invite her to tea.”
As far as I know, the usual way to build a negative sentence in English is to use do/does not, so I was surprised to see such a sentence.
Why don't "She doesn't know about it."? When should we use the "be not to" construction?
Contemporary American English usage includes a participle to convey this idea. Possible options include:
The same idea can be expressed with a modal auxiliary:
This is a different idea than the one expressed by "She does not know about it". Since it's followed by "Gatsby doesn't want her to know," I take it to mean something like "She doesn't have permission to know about it. Gatsby is withholding permission." The implication of the overall passage is "You don't have permission to tell her."
