Q. When a character in a novel or story is speaking and pauses or falters between two sentences, and that pause is indicated with an ellipsis, is it correct or incorrect to add a period after the first sentence?
A. In fiction the convention is to limit ellipses to three dots—whether the ellipsis follows a complete sentence or not, and whether the ellipsis indicates a faltering or trailing off or a more definite pause. This convention applies equally to dialogue and narration. Following the ellipsis, you can use a capital letter to indicate the start of a new sentence, especially to signal a definite shift (as in the fourth example):
“Will . . . will you help me?” It took all his courage to ask.
“Don’t try to help me . . . just don’t.” Dylan wouldn’t even look at us.
“Don’t try to help me . . . you wouldn’t understand.”
We had so many adventures . . . It’s sad that they’re now done.
Though a sentence-ending period isn’t retained with an ellipsis, a question mark or an exclamation point is. The placement of these marks relative to the ellipsis will depend on context and emphasis:
“Stop! . . . Stop, I tell you!” The chase was on.
“So you’re married . . . !” He waited in vain for his friend to deny it.
“So you’re married . . . ?” The question hung in the air.
For some additional considerations, see “Prose, Interrupted: Signaling Breaks in Dialogue,” at CMOS Shop Talk. For the use of ellipses to indicate omissions, in which case a period is usually retained before an ellipsis at the end of a sentence, see CMOS 13.50–58.