The scratch on the safe door, slight and minute as it was, was his starting-point. How had it been made? He had found by experiment that it was impossible to make such a scratch upon the varnish without the exercise of considerable force. It was clear, therefore, that the scratch by the keyhole could not have been made by the thief in his trembling anxiety to get the business he had undertaken accomplished. But why was such force used?
For a long time Lecoq puzzled over this problem. Then, with Fanferlot, he tried an experiment. In his room was an iron box varnished like the safe. Taking the key of this box from his pocket, he ordered Fanferlot to seize his arm just as he put it near the lock. The key slipped, pulled away from the lock, and sliding along the surface of the door, left upon it a diagonal scratch, almost an exact reproduction of the one on the safe.
From this simple experiment Lecoq deduced that two people were present when the safe was robbed; one wanted to take the money, the other wanted to prevent it being taken. This was the basis of the case which he set out to draw up against some person or persons unknown. He argued, with his usual clear logic, that neither Fauvel nor Bertomy could have robbed the safe. Both of them had keys; both of them knew the secret word and could have robbed the safe whenever they pleased. Therefore, neither of them would have committed the theft in the presence of somebody else.
II.--A Mysterious Journey
Lecoq's first steps after establishing these preliminary deductions was to secure the release of Bertomy on the grounds of insufficient evidence.
On the very morning of his release, Bertomy had received a mysterious letter composed of printed words cut out letter by letter from a book and pasted on paper.
"My dear Prosper," so the epistle ran, "a friend who knows the horror of your situation sends you this help. There is one heart at least which feels for you. Leave France; you are yourself. The future is before you. Go, and may this money be of use."
Enclosed with this note were banknotes for £400. Lecoq, disguised as a M. Verduret, a country merchant, a friend of Bertomy's father, secured this epistle and studied it carefully. His knowledge of the various types used by the printers in Paris showed him that the letters had been taken from a book printed by a well-known firm who published volumes of devotion. The correctness of this conclusion was established by the discovery on the back of one of the small cuttings the word "Deus." The words had been cut from a Catholic prayer-book. To find that prayer-book was his next business.
In another disguise he sought out Nina Gipsy, and, by asking her assistance to clear Prosper, induced her to take up the position of lady's-maid in the Fauvel family, for it was there, he conceived, the mutilated book of devotion would be found. Again his wonderful instinct proved right. In a few days Nina brought him the very book--a prayer-book, belonging to Madeline, which had been given her by Bertomy.
Why had Madeline sent the cashier this elaborately disguised letter? Why had she wished him to leave France, confident as she was, so she told him, of his innocence?