The Door With Seven Locks by Edgar Wallace

WHILST THE ladies were walking in the park after tea, Dick went from room to room and made a very thorough examination of windows and walls. He had procured a builder's tape measure, and, with the assistance of one of the police officers who had arrived from London, he measured the room both inside and out, and compared his figures with those he obtained from the two apartments which flanked the state chamber. The difference was so slight as to preclude any possibility of there being a secret passage between the walls. These, as is usual in the Elizabethan buildings, were very thick and seemed solid enough.

The state apartment was a large room, rather overpoweringly furnished, with an old-fashioned four-poster bed set upon a dais. The walls were hung with tapestries; a few old pieces of furniture comprised its contents, and had the floor been covered with rushes it might have stood for an Elizabethan bedroom without one modern touch.