Considerably mystified, he tried to open the door. It was locked, and though with his wire he eventually shot back the bolt, the trouble he had, proved that the lock was one of first quality. Indeed, it was not a cupboard lock screwed to the inside of the door as might have been expected, but a small-sized mortice lock hidden in the thickness of the wood, and the keyhole came through to the inside; just the same arrangement as is usual in internal house doors.

The inside of the wardrobe revealed nothing of interest. Two coats and waistcoats, a sweater, and some other clothes were hanging from hooks at the back. Otherwise the space was empty.

“Why,” he wondered as he stood staring in, “should it be necessary to lock up clothes like these?”

His eyes turned to the drawer below, and he seized the handles and gave a sharp pull. The drawer was evidently locked. Once again he produced his wire, but for the first time it failed him. He flashed a beam from his lamp into the hole, and then he saw the reason.

The hole was a dummy. It entered the wood but did not go through it. It was not connected to a lock.

He passed the light round the edges of the drawer. If there was no lock to fasten it why had he been unable to open it? He took out his penknife and tried to push the blade into the surrounding space. It would not penetrate, and he saw that there was no space, but merely a cut half an inch deep in the wood. There was no drawer. What seemed a drawer was merely a blind panel.

Inspector Willis grew more and more interested. He could not see why all that space should be wasted, as it was clear from the way in which the wardrobe was finished that economy in construction had not been the motive.

Once again he opened the door of the upper portion, and putting his head inside passed the beam of the lamp over the floor. This time he gave a little snort of triumph. The floor did not fit tight to the sides. All round was a space of some eighth of an inch.

“The trap-door at last,” he muttered, as he began to feel about for some hidden spring. At last, pressing down on one end of the floor, he found that it sank and the other end rose in the air, revealing a square of inky blackness out of which poured a stream of cold, damp air, and through which he could hear, with the echoing sound peculiar to vaults, the splashing and churning of the sea.

His torch revealed a flight of steps leading down into the darkness. Having examined the pivoted floor to make sure there was no secret catch which could fasten and imprison him below, he stepped on to the ladder and began to descend. Then the significance of the mortice lock in the wardrobe door occurred to him, and he stopped, drew the door to behind him, and with his wire locked it. Descending farther he allowed the floor to drop gently into place above his head, thus leaving no trace of his passage.