Missing spoken line in conversation "Stuff of Legend"

When I saw the conversation "Stuff of Legend", there was an odd silence after Arwin Merton's voiced line. The camera stayed on him, and he had animation happening for perhaps two seconds (idle animations, not speaking, I think). Then he resumed talking. I checked the conversation log. One line was missing from what was spoken.

There's a monster - I know that. (spoken)

What is it? (missing)

That, I don't know. (spoken)