I smiled at my own innocence when I remembered how completely he had imposed upon me by showing me his papers of identity, and the photographs of his pretended family. Truly only a great criminal could have remained so imperturbed and polite to the man whom he intended should die. "This drug orosin is a very mysterious one, I suppose?" I remarked a few seconds later as the Professor, who had offered me a cigar, was in the act of lighting up. "Yes. A very weak solution taken by the mouth produces extraordinary effects upon the human brain. The latter almost instantly becomes unbalanced and the victim lapses into an unconscious state for days, even for weeks," he said. "Very often the brain is quite normal, save that a complete loss of memory follows the return to consciousness. In other cases orosin has produced complete and hopeless dementia." "Always hopeless?" I asked eagerly, recollecting my own case and that of Gabrielle Tennison. "Not always hopeless. There have been cases that have been cured." "Do you know any personally?" I demanded breathlessly. "There are one or two--very few--on record. Professor Gourbeil, the well-known alienist of Lyons, has observed two patients who recovered. But the majority of cases where orosin has been administered were found incurable. The mind is blank, the memory completely destroyed, and the general health so undermined that only the strongest persons can withstand the strain." At once I described Gabrielle's symptoms and general attitude, whereupon the Professor said: "What you tell me are the exact symptoms exhibited by a person to whom a small dose of orosin has been administered. In most cases, however, such a state of mind develops into actual insanity with a homicidal tendency. Such a patient should be very carefully watched, for in ninety per cent. the chance of a cure is, alas! beyond expectation." CHAPTER THE EIGHTEENTH MORE ABOUT THE MYSTERY-MAN One very important fact I had established. Orosin was the obscure and little-known drug that had been administered to Gabrielle Tennison, as well as to myself, by the mystery-man of Europe at his palatial house in Stretton Street. Gabrielle being the weaker, was still suffering from its paralysing effects, while I, the stronger, had practically recovered. Yet it had been intended by the daring Despujol that a fatal "accident" should now befall me! And could anything be plainer than that the fellow for whom the police were searching so eagerly was a hireling of the man De Gex who went in fear of me? That most secret and most potent of all poisons might be known to Moroni! Indeed, it apparently was known to him, and the endeavour had been to introduce it into my system by means of an infected carpet pin. On leaving Professor Vega I at once sent a note round to Hambledon, and awaited his arrival. When he came I related all the professor had told me.