punctuation if dash introduces question-sentences

He worried--why X; what will happen if Y?

It seems that this construction expresses the idea best, but it creates a few punctuation questions.

Should the first semicolon be question-mark? Is there also a past-present tense shift issue in the above?

Should W in why and what be capitalized? (typically one doesn't capitalize after dash but here dash introduces two sentences)

Here are some variations that illustrate the issue with 2 sentences that follow emdash and are supposed to connected to the clause before the emdash.

He worried--why X? What will happen if Y?

He worried--why X? what will happen if Y? (incorrect: can't have smallcase following '?')

He worried--Why X? What will happen if Y? (incorrect: can't have capitalcase following '--')

He worried--why X; what will happen if Y? (this can perhaps be a good way to express connecting the 2 sentences to the dash)

He worried--why X; What will happen if Y? (incorrect: can't have capital following semicolon)

Some have suggested using ':' instead of dash '--'. It's perhaps a more convenient option as rules regarding capitalization are more clearly defined for ':' but it doesn't fit in the context of where this expression is needed.

He worried: Why X; What will happen if Y? (this is perfectly acceptable. One can certainly capitalize right after colon if it begins a sentence. However as said earlier, this is ':' doesn't fit the context)

Solution 1:

Normally, direct speech should be quoted. But, as pointed out by Edwin Ashworth, thought are somewhat of an edge case so you may choose:

• either process it as direct speech, and quote it (you are quoting your character).
• or simply include it within the normal rhythm of the text.

Quoting:

He worried: “Why X; what will happen if Y?”

• You quote a full sentence, so it takes a capital.
• You quote a full sentence, so usually you keep the ? inside the quotes.
• Semicolon is fine. A bit unusual, but correct.
• You do not normally use dashes for direct speech in English, but quotation marks.
• You may choose single quotes over double quotes. One usually finds the former in British conventions and the latter in American conventions, but it does not matter as long as your are consistent.
• Some authors do use dashes in modern writings though. It is often considered bad style. Anyway, when they do so, it always starts a new paragraph, like this:

He worried:

― Why X; what will happen if Y?

Notice the long dash in that case: ― (unicode U+2015), not - (minus).

Keep in mind that this is borrowed from foreign languages, and as such it does not follow the usual rules for dashes in English. In proper English, dashes are only used for interruptions in a sentence: marking a pause, introducing a subsidiary idea, etc.

Including in normal rhythm:

He worried: why X… what will happen if Y?

He worried: why X? what will happen if Y?

If I chose it not to be a quote, I would not put capital letters either, for it is no longer an independent sentence. But according to Edwin Ashworth you can get away with capitals too.

For reference, see this pretty thorough punctuation guide.