'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.'