near Piccadilly Circus.

He was in London with a warrant for the arrest of Mateo Sanz in his
pocket. But at my suggestion he stayed his hand. Meanwhile Sanz, all
unsuspecting, was being carefully watched, not only by two
detective-sergeants from Scotland Yard, but also by two Spanish
detectives whom Rivero had brought to London with him.

Two days later, in response to a message from Rivero, I called at the
Hotel Cecil on leaving the office. He met me in the marble-paved
entrance hall, and I noticed at once a grave expression upon his face.

"Come up to my room," he said in French. "We can talk quietly there."

In surprise I went with him up in the lift to the third floor where,
in a bedroom which overlooked the Embankment and the Thames beyond, he
turned suddenly to me and exclaimed, still in French:

"I am very troubled and mystified, Monsieur Garfield. When you made
those curious allegations against Monsieur De Gex I confess that I
laughed them to scorn, but I have to-day learned several facts which
put an entirely fresh complexion upon the present circumstances. Last
night Mateo Sanz visited De Gex again. The financier gave a musical
evening, but after the departure of all the guests, Sanz called and
was at once admitted to De Gex's library."

"Ah!" I exclaimed. "I know that room. I have sad cause to remember
it!"

"He remained there till nearly two o'clock in the morning. Then he
returned on foot to his hotel. My information is that on his walk back
he was whistling to himself, as though in high spirits."

"But that is surely no extraordinary circumstance!" I remarked. "Did I
not tell you that De Gex is as friendly with Sanz as he was with
Despujol?"

"I know. But in face of other facts I have learnt, the problem
presented is an amazing one."

As he spoke a tap came upon the door, and a page-boy handed in a card.

"Show the gentleman up," Rivero said in his broken English.

"Here is someone who will relate some very strange facts. He is my
friend Gonzalez Maura, an advocate who practised in Madrid before his
appointment to our Consulate here. I called at the Consulate yesterday
and saw him, when he related to me some curious facts which I have
asked him to repeat to you. He is here for that purpose."

A few moments later the page-boy ushered in a middle-aged,
well-dressed, black-bearded man who bowed elegantly when we were
introduced.

"Now, my dear friend," exclaimed Rivero, when we were all thre