‘The time-lock!  Someone must have set it!’ cried the patrol to Shawn, and the two hastened to the other end of the main corridor, where the dial of the machine glistened under an electric lamp.

And all the sub-guardians stirred and grumbled in their beautiful bright cages like wrathful lions.  No such scene had ever been known in that Safe Deposit or any other safe deposit before.

The patrol was right.  The dial of the time-lock showed that it had been set against every lock, great and small, in the Safe Deposit, until nine a.m. the next day.

‘It’s all up!’ the patrol said solemnly.

’Do you mean to say nothing can be done to open that vault till nine to-morrow?’ Simon demanded in despair.

’Nothing.  The blooming Czar couldn’t manage it with all his Cossacks!  No, nor Bobs either!  This is a Safe Deposit, this is, and if Mr. Hugo is in that vault, it’s Mr. Hugo as knows it’s a Safe Deposit by now.’

A brief silence ensued, and then Simon said: 

’We must telephone to the police.  There’s a telephone in the waiting-room, isn’t there?’

The patrol admitted that there was, but his manner hinted a low opinion of the utility of the police.  He stood mute while Simon Shawn told the telephone receiver what had occurred in the bowels of the earth beneath Hugo’s.

‘Wait a minute,’ said the telephone, and then, after a pause:  ’Are you there?  I’m Inspector Winter.’

‘That’s him as has charge of all the strong-room cases,’ the patrol interjected to Simon.

‘I’ve got Mr. Jack Galpin here, as it happens,’ said the telephone.

‘Mr. Jack Galpin?’ Simon questioned.

‘He’s just done eighteen months for an attempt in Lombard Street,’ the patrol explained.  ‘I’ve heard of him.’

‘I’ll come down with him immediately in a cab,’ said the telephone.

When Simon returned to the impregnable door of Vault 39 he listened in vain for a sound.  Then he knocked with his pen-knife on the polished steel, and presently there was an answering signal from within—­a series of scarcely perceptible irregular taps.  It struck him that the irregularity of the taps formed a rhythm, and after a few seconds he recognised the rhythm of the Intermezzo from ‘Cavalleria Rusticana,’ which he had played for Hugo that very morning.

It was at this moment that the messenger-boy attached to the department came whistling into the steel corridors, and delivered to the patrol a small white packet, which, he said, Mr. Brown had handed to him with instructions to hand it to the patrol.  He had seen Mr. Brown in a cab outside the building, and Mr. Brown had the appearance of being very ill.

The packet contained the second key of Vault 39.

‘But this’ll be no use till to-morrow,’ was the patrol’s comment, ’and by then—­’

CHAPTER XIII