But Barty saw where Sirius eyes strayed and he backed away with a smile, his wand drawn.

"Morsmordre." The word is just whispered, but his Lord's sign appears above them sure enough, the skull and the snake moving against the ceiling, the green light shining through even with closed eyes. Making sure Sirius couldn't keep pretending to be anywhere else but here.

And that done, Barty just continued where he left off, taking Sirius into his mouth while he ran his nails down his thigh, leaving red streaks.