Bella gives you a little nod - though not of a concurring conclusion, as much as a willingness to back yours. It's hard to overlook the visual awfulness of the scenario, in which Margot is definitely the one suffering most. Donallo, at least, is free to move about his home. But whichever of them it is that is so afflicted, they act the part of the innocent very well; both man and wife look comprehensively miserable: Donallo, like a man who has been reduced from a local Lord to a wretched steward over a his afflicted wife to preserve her from public exposure and destruction, and Margot like a woman whose beloved had one day become a monster and kept her a prisoner in the chambers in which she once felt safe and treasured for the satisfaction of what daemonic cruelty required her confinement.

Briant looks anguished - these are his father's friends; his own friends, by inheritance. As a good example of the knightly ideal, Briant paces and fumes as he is now confronted with an evil and injustice which is not presenting a clean and clear solution. If only this were, instead, another hundred goblins with necks that could be cut, or wrung.

"You are probably right. But how to proceed..? I have never - ... I have only ever heard whispers of daemons. I do not know what to expect of them, and their powers. But... Remember Bertuccio, and his imposter..? When we didn't know which was true. What did the Matrona, and Simonuccio="

She pauses to spit on the floor.

"What did they do, seeking the truth...? We should... separate them. Ask them questions; see perhaps if one knows something another does not, or... something that can't be corroborated."

Briant, whose grasp of Tilean is improving by increments, gets enough of this through the filter of your gun pointed at Donallo. He grimaces, almost literally struggling to swallow the next action, before pointing his sword at Donallo.

"Rends-toi, Donallo. Je vais vous lier, dans une autre pièce. Prions que la Dame nous donne la sagesse de voir à travers cela de l'autre côté."

Donallo objects, naturally - he needs help, not incarceration, and you see his eyes track to the door behind as if considering running, or how far away his few men-at-arms might be. But after an arguement with Donallo, and through Margot's repeated plea to do him no harm, the man lets Briant bind his wrists, and leads him away to guest room to secure him.

Spoiler: OOC:
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It's a fun puzzle! Put on your sleuthing hat, detective; there's a mystery at foot. Which of these nobles is a victim of extradimensional possession, and which is merely the suffering recipient of a tremendously cruel twist of fate to be married to such? And is the cure fire in large amounts? Jinkies!

You can ask whichever one you like whatever questions you like, or subject then to whatever deceptions you can muster. You may also explore the keep, if you're looking for something specific or corroborating, or speak to the ogres or the men-at-arms. Feel free to make any roll you think is appropriate.