a short black beard when he got out of the cab,' he replied.

'What do you mean by that?'

'I drive a closed cab, sir. When he got in he was a smooth-faced
gentleman; when he got out he wore a short black beard.'

'Was he a Frenchman?'

'No, sir; he was a foreigner, either English or American.'

'Was he carrying a box?'

'No, sir; he held in his hand a small leather bag.'

'Where did he tell you to drive?'

'He told me to follow the cab in front, which had just driven off very
rapidly towards the Madeleine. In fact, I heard the man, such as you
describe, order the other cabman to drive to the Madeleine. I had come
alongside the curb when this man held up his hand for a cab, but the
open cab cut in ahead of me. Just then my passenger stepped up and
said in French, but with a foreign accent: "Follow that cab wherever
it goes."'

I turned with some indignation to my inefficient spy.

'You told me,' I said, 'that the American had gone down a side street.
Yet he evidently met a second man, obtained from him the handbag,
turned back, and got into the closed cab directly behind you.'

'Well, sir,' stammered the spy, 'I could not look in two directions at
the same time. The American certainly went down the side street, but
of course I watched the cab which contained the jewels.'

'And you saw nothing of the closed cab right at your elbow?'

'The boulevard was full of cabs, sir, and the pavement crowded with
passers-by, as it always is at that hour of the day, and I have only
two eyes in my head.'

'I am glad to know you had that many, for I was beginning to think you
were blind.'

Although I said this, I knew in my heart it was useless to censure the
poor wretch, for the fault was entirely my own in not sending two men,
and in failing to guess the possibility of the jewels and their owner
being separated. Besides, here was a clue to my hand at last, and no
time must be lost in following it up. So I continued my interrogation
of the cabman.

'The other cab was an open vehicle, you say?'

'Yes, sir.'

'You succeeded in following it?'

'Oh, yes, sir. At the Madeleine the man in front redirected the
coachman, who turned to the left and drove to the Place de la
Concorde, then up the Champs-Elysees to the Arch and so down the
Avenue de la Grande Armee, and the Avenue de Neuilly, to the Pont de
Neuilly, where it came to a standstill. My fare got out, and I saw he
now wore a short black beard, which he had evi