After a long calculation the Consul suddenly raised his face to me and said—­

“Then six ten shilling ones have been taken!”

“Why?  There must be some motive!”

“They are of no use to anyone except to Consuls,” he explained.  “Perhaps they were wanted to affix to some false certificate.  See,” he added, opening the portfolio, “there were six stamps here, and all are gone.”

“But they would have to be obliterated by the Consular stamp,” remarked Cavendish.

“Ah! of course,” exclaimed Hutcheson, taking out the brass seal from the safe and examining it minutely.  “By Jove!” he cried a second later, “it’s been used!  They’ve stamped some document with it.  Look!  They’ve used the wrong ink-pad!  Can’t you see that there’s violet upon it, while we always use the black pad!”

I took it in my hand, and there, sure enough, I saw traces of violet ink upon it—­the ink of the pad for the date-stamp upon the Consul’s table.

“Then some document has been stamped and sealed!” I gasped.

“Yes.  And my signature forged to it, no doubt.  They’ve fabricated some certificate or other which, bearing the stamp, seal and signature of the Consulate, will be accepted as a legal document.  I wonder what it is?”

“Ah!” I said.  “I wonder!” And the three of us looked at each other in sheer bewilderment.

“The reason the papers are all upset is because they were evidently in search of some blank form or other, which they hoped to find,” remarked my friend.  “As you say, the whole affair was most carefully and ingeniously planned.”

We crossed the great sunlit piazza together and entered the Questura, that sun-blanched old palace with its long cool loggia where the sentry paces day and night.  The Chief of Police, whom we saw, had no further information.  The mysterious yacht had not put in at any Italian port.  From him, however, we learned the name of the detective who had seen the two strangers leave Leghorn by the early morning train, and an hour afterwards the police-officer, a black-eyed man short of stature, but of an intelligent type, sat in the Consulate replying to our questions.

“As far as I could make out, signore,” he said, “the man was an Englishman, wearing a soft black felt hat and a suit of dark blue serge.  He had hair just turning gray, a small dark mustache and rather high cheek-bones.  In his hand he carried a small bag of tan leather of that square English shape.  He seemed in no hurry, for he was calmly smoking a cigarette as he went across to the ticket office.”

“And his companion?” asked the Consul.

“She was in black.  Rather tall and slim.  Her hair was fair, I noticed, but she wore a black veil which concealed her features.”

“Was she young or old?”

“Young—­from her figure,” replied the police agent.  “As she passed me her eyes met mine, and I thought I saw a strange fixed kind of glare in them—­the look of a woman filled with some unspeakable horror.”