The panel slid aside.

Edgar and Gaydon stepped into a little cabinet lighted by a single window.

The room was empty.
Gaydon took a peep out of the window and saw the Tiber eddying beneath.
Edgar went to a corner and touched a spring.

The stone slab rose from its grooves; the panel slid back across it; at the same moment the door of the room was opened, and the Chevalier stepped across the threshold.
Gaydon could no longer even pretend to doubt who had walked with Whittington to the Caprara Palace the night before.

It was none of his business, however, he assured himself.