And this is why she normally tries to knock people out.

The flow of mana is abruptly cut off, but not before several pages fill with Negi's lesser and not-so-lesser spells. Signum blinks in surprise as she watches it cut off. "A fail-safe?" she wonders aloud.

She quickly grabs the Book again and pauses for a few seconds, ready to see if he had any followup to that.