Bab 46: 45. Come back.

On the top floor of a gigantic Victorian mansion concealed in the depth of the forest, ahem- in the surburbs of the town surrounded by tall trees, a medium seized ball of light formed a barrier around a room. It was made up a faint purple light which can not be seen by the naked human eye. 

Even for a demon, it would take a higher rank to be able to notice it.

It was a necessary precaution the occupants of the room took against the blasting sounds coming from within which was absorbed and dismissed by the medium.