[It's a face that lasts only for a moment. A simple, gobsmacked moment before Carmilla is back to fire and fury, saying nothing but communicating how dare you with every inch of her being. Alucard watches this, and then it becomes clear what they can do.

There's other ways to track the flow of this awful medicine after all.

When Alucard holds up a hand, there's no released tension from the room.]

Then that means your own blood has been used to paint you as an enemy of this House, and whoever is responsible has been far too bold with the nature of this crime. [Here is the trick.]

Blood has always called to blood. We can track the matter through that same blood, should you allow it, and justice can take it's course as it must.