Here is the letter, published by the newspapers, which also published the declarations of the experts certifying that the handwriting was Hippolyte Fauville's:
"I have seen him! You understand, don't you, my dear friend? I have seen him! He was walking along a path in the Bois, with his coat collar turned up and his hat pulled over his ears. I don't think that he saw me. It was almost dark. But I knew him at once. I knew the silver handle of his ebony stick. It was he beyond a doubt, the scoundrel!
"So he is in Paris, in spite of his promise. Gaston Sauverand is in Paris! Do you understand the terrible significance of that fact? If he is in Paris, it means that he intends to act. If he is in Paris, it means certain death to me. Oh, the harm which I shall have suffered at that man's hands! He has already robbed me of my happiness; and now he wants my life. I am terrified."
So Fauville knew that the man with the ebony walking-stick, that Gaston Sauverand, was designing to kill him. Fauville declared it most positively, by evidence written in his own hand; and the letter, moreover, corroborating the words that had escaped Gaston Sauverand at his arrest, showed that the two men had at one time had relations with each other, that they were no longer friends, and that Gaston Sauverand had promised never to come to Paris.
A little light was therefore being shed on the darkness of the Mornington case. But, on the other hand, how inconceivable was the mystery of that letter found on the table in the workroom!
Five men had kept watch, five of the smartest men obtainable; and yet, on that night, as on the night of the fifteenth of April, an unknown hand had delivered the letter in a room with barricaded doors and windows, without their hearing a sound or discovering any signs that the fastenings of the doors or windows had been tampered with.
The theory of a secret outlet was at once raised, but had to be abandoned after a careful examination of the walls and after an interview with the contractor who had built the house, from Fauville's own plans, some years ago.
It is unnecessary once more to recall what I may describe as the flurry of the public. The deed, in the circumstances, assumed the appearance of a sleight-of-hand trick. People felt tempted to look upon it as the recreation of some wonderfully skilful conjurer rather than as the act of a person employing unknown methods.
Nevertheless, Don Luis Perenna's intelligence was justified at all points, for the expected incident had taken place on the twenty-fifth of April, as on the fifteenth. Would the series be continued on the fifth of May? No one doubted it, because Don Luis had said so and because everybody felt that Don Luis could not be mistaken. All through the night of the fifth of May there was a crowd on the Boulevard Suchet; and quidnuncs and night birds of every kind came trooping up to hear the latest news.
The Prefect of Police, greatly impressed by the first two miracles, had determined to see the next one for himself, and was present in person on the third night.