t-well.

Now, it was a singular thing that when Simon Shawn, having proved his
identity and his mission at the lift, arrived at the entrance to the
Safe Deposit, he discovered the great steel door ajar, and no
door-guardian in the leather chair where a door-guardian always sat.
This condition of affairs did not affect the essential impregnability of
any individual vault or safe, but, nevertheless, it was singular.

Simon walked straight in.

'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?'

'Mr. Hugo.'

'It's God help him, then,' said the patrol, 'if he's there long. There's
no ventilation, Mr. Shawn. We'd better telephone for Mr. Polycarp. The
other key will be in the key-safe. I can get it. But how do you make
out, sir, that Mr. Hugo can be in there? The vault could only be locked
by Mr. Polycarp and Mr. Brown together, and surely they couldn't both--'

'Mr. Polycarp left his keys behind by accident. He had gone before Mr.
Hugo came down.'

'There's been no Mr. Polycarp here this morning,' said the patrol a
minute later. 'I've looked at the signatu