As I have already observed, when the crime had become known, the permanent detective force had been most assiduous in the attentions they had given it.  The only piece of valuable evidence, however, that they had been able to accumulate, was a footprint on a flower-bed near the centre of the yard, and another in the hall of the house itself.  Now it was definitely settled, by a careful comparison of these imprints, that the murderer, whoever he might have been, wore his boots down considerably on the left heel, and on the inside.  Now, as every bootmaker will tell you, while the outer is often affected in this way, the inner side seldom is.  I noticed, however, that this was the case with the man I suspected.  The heel of his left boot was very much worn down and on the inside.  The right, however, was intact.

On leaving the Continental Hotel, I made my way to the Police Commissioner’s office, obtained an interview with him, and placed the evidence I had gleaned before him.  He was good enough to express his approval of my endeavours, but was doubtful whether the case against the Italian was strong enough yet to enable us to definitely bring the crime home to the man.

“At any rate it will justify our issuing a warrant for his arrest,” he said, “and that had better be done with as little delay as possible.  Otherwise he will be out of the country.”

A warrant was immediately procured and an officer was detailed to accompany me in case I should need his assistance.  When we reached the Continental Hotel I inquired for Senor Gairdi, only to be informed that he had left the hotel soon after lunch.

“It is only what I expected,” I said to my companion.  “His suspicions are aroused, and he is going to try and give us the slip.”

“I think not,” said the manager.  “I fancy you will find that he is on board the steamer.  You must remember that she sails at daybreak.”

We accordingly hastened to the river, and made our way to where the steamer was lying.  On arrival on board I inquired for the head-steward, and when he put in an appearance inquired whether Senor Gairdi had come aboard yet.

“He brought his luggage on board, and inspected his cabin about three o’clock,” that official replied, “and then went ashore again.”

There was nothing for it therefore but for us to await his return.  Though we did not know it, we were in for a long spell, for it was not until nearly nine o’clock that our man reappeared on board.  He had just crossed the gangway and was making his way along the promenade deck, when I accosted him.

“May I have a word with you, Senor Gairdi?” I asked.

“Yes, certainly,” he replied, speaking with only a slight foreign accent.  “What is it you want?”

I drew him a few paces further along the deck, so that, if possible, the other passengers, who were standing near, should not hear what I had to say to him.

“I have to tell you,” I said, “that I hold a warrant for your arrest on the charge of murdering one, Joseph Spainton, on the night of July the nineteenth of this year.  I must caution you that anything you may say will be used as evidence against you.”