He was privately of opinion that the whole affair was a practical joke or a fraud, and waited an opportunity of catching the rogue _flagrante delicto_.

He did not long keep this theory to himself, but let it out by degrees with no stint of oaths and threats, believing that some domestic traitor held the thread of the conspiracy.
Indeed it was time something were done; for not only his servants, but good Mrs.Prosser herself, had grown to look unhappy and anxious.

They kept at home from the hour of sunset, and would not venture about the house after night-fall, except in couples.
The knocking had ceased for about a week; when one night, Mrs.Prosser being in the nursery, her husband, who was in the parlour, heard it begin very softly at the hall-door.

The air was quite still, which favoured his hearing distinctly.

This was the first time there had been any disturbance at that side of the house, and the character of the summons was changed.
Mr.Prosser, leaving the parlour-door open, it seems, went quietly into the hall.