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 MR. GALPIN When the patrol and Simon between them had explained the mysterious and fatal situation to Mr. Jack Galpin, Mr. Jack Galpin leaned against one of the marble tables in the waiting-room, and roared with laughter. 'Well,' observed Mr. Galpin, 'he didn't have his Safe Deposit built for nothing, anyhow!' And he laughed again. 'But he's slowly dying in there!' said Simon. 'Yes, I know,' said Mr. Galpin. 'That's what makes it such a good joke.' 'I don't see it, sir,' Simon remarked. 'Simply because your sense of humour is a bit off. What are you?' 'I am Mr. Hugo's man.' 'My respects.' Mr. Galpin had arrived with Inspector Winter, and Inspector Winter had introduced him as knowing more about safes than any other man in England, or perhaps in Europe. After the introduction, Inspector Winter, being pressed for time, had departed. Mr. Galpin was aged about forty, and looked like an extremely successful commercial traveller. No one would have suspected that he had recently done eighteen months anywhere but in a first-class hotel; even his thin hands were white, and if his hair was a little short--well, the hair of very many respectable persons is often a little short. It appeared that he was under obligations to Inspector Winter, and anxious to oblige. The relations between distinguished law-breakers and distinguished detectives are frequently such as can only exist between artists who esteem each other. For the rest, Mr. Galpin had brought a brown bag. 'You see, the time-lock is placed so that--' began the patrol. 'Shut up!' said Mr. Galpin curtly. 'I know all that. I've got scale-plans of every Safe Deposit in London, and I decided long since that this one was too good to try. Of course, with the aid of the entire staff things might be a bit easier, but not much--not much!' he repeated scornfully. 'If I can manage a job at all, I can usually manage it alone, and in spite of the entire staff.'