midnight
` Well , I can assure you that the Lord of Rantremly who lives in London knows nothing about it . I have been up and about since daylight , taking some rough measurements by stepping off distances . I surmise that the secret room is to the left of this stairway . Probably a whole suite of rooms exists , for there is certainly a stair coinciding with this one , and up that stair at midnight I heard a club-footed man ascend . Either that , or the ghost that has frightened you all , and , as I have said , I believe in the man . ' Here the official made the first sensible remark I had yet heard him utter : -- ` If the walls are so thick that a prisoner 's cry has not been heard , how could you hear his footsteps , which make much less noise ? ' ` That is very well put , constable , and when the same thing occurred to me earlier this morning , I began to study the architecture of this castle .