"What sort of task?" is the next question, naturally. Dorian is cautious as he asks, confusion and concern and a growing sense of dread make him feel slightly ill, despite his attempts to rationalize.

He reaches for Bull's arm, both to steady himself and as a solid point of contact between them. He sees what Bull is getting at. If someone has been following them, then that someone has to be good enough at what they do to avoid the Bull's notice, which is no easy feat. It's mildly horrifying. When had they been able to get close enough to deposit the note? Had they been together then? Had they been asleep?

"We should assume that it's...that someone knows." Whether it's Bull's faction, his own, or another entirely.