'There's no one at the door,' he said to the patrol, whom he met in the main passage. 'I want to see Mr. Hugo at once. He's down here somewhere, or he's been here.'
'Yes, Mr. Shawn,' said the patrol politely; 'I did see Mr. Hugo here about an hour or so ago. I'll ask Mr. Brown. Will you step into the waiting-room?'
Half-way along the main corridor was a large room, whose steel walls were masked by tapestries, where renters could examine their treasures on marble tables. It was empty when Simon went in. The patrol carefully closed the door on him, and then in a moment came back to say that Mr. Brown was not in his office, and had probably gone out to lunch, the hour being noon.
'Where did you see Mr. Hugo?' Simon asked, hurrying out of the room in a state of considerable agitation.
'I saw him just here, sir,' said the patrol, turning down a short side corridor—the grille was unfastened—and stopping before a door numbered thirty-nine. 'He was talking to Mr. Brown, and the door of the vault was open.'
'That must be Mr. Polycarp's vault,' Simon observed; and then he started, and put his ear against the door. 'Listen!' he exclaimed to the patrol. 'Can't you hear anything inside?'
And the patrol also put his ear to the steel face of the door.
'I seem to hear a faint knocking, but it's that faint as you scarcely can hear it. There! it's stopped.'
'He is inside,' Shawn whispered.
'Who's inside?'