"And you have discovered the truth?" I demanded.

"Yes," he responded, turning down the flame of the lamp and bending attentively to the bubbling fluid from which all colour had disappeared while I had been watching. "Shall I relate to you the course of my investigations?"

"Do. I am all attention."

"Well," he said, leaning both elbows upon the table and resting his chin upon his hands, while the tame brown rat ran along the table and scrambled into his pocket, "on the first evening you sought my a.s.sistance I knew, from the remote effects which both of us experienced, that the evil influence of that mysterious visitor in black, was due to some unknown neurotic poison. It was for that reason that I was enabled to administer an antidote without making an exact diagnosis. Now, as you are well aware, toxicology is a very strange study. Even common table-salt is a poison, and has caused death. But my own experiments have proved that, although the various narcotic poisons produce but little local change, their remote effects are very remarkable. Certain substances affect certain organs in particular. The remote action of a poison may be said to be due, in every instance, to its absorption into the veins or lymphatics, except when there is a direct continuity of effect traceable from the point where the poison was applied to the point where the remote effect is shown. It is remarkable that the agents which most affect the nervous system do not act at all when applied to the brain or trunks of nerves. Poisonous effects result from absorption of the poisoning body, and absorption implies solution; the more soluble, therefore, the compound is, the more speedy are its effects. Do you follow me?"

"Quite clearly."

"The rapid, remote effect produced on leaving that room made it plain that I must look for some powerful neurotic poison that may be absorbed through the skin," he went on. "With this object I searched microscopically various objects within and without the room, but for a long time was unsuccessful, when, one morning, I made a discovery that upon the white porcelain handle of the door a little colourless liquid had been applied. Greater part of it had disappeared by constant handling, but there was still some remaining on the shaft of the handle, and the microscope showed distinct prism-shaped crystals. All these I secured, and with them have since been experimenting. I found them to be a more deadly poison than any of the known paralysants or hyposthenisants, with an effect of muscular paralysis very similar to that produced by curare, combined with the stiffness about the neck and inability to move the jaws so apparent in symptoms provoked by strychnia. The unknown substance--a most deadly, secret poison, and, as I have since proved, one of those known to the ancients--had been applied to the door-handle on the inside, so that any person in pulling open the door to go out must absorb it in sufficient quant.i.ty to prove fatal. Indeed, had it not been for the antidote of chlorine and the mixed oxides of iron which I fortunately hit upon, death must have ensued in the case of each of us.

"To determine exactly what was the poison used was an almost insurmountable task, for I had never met with the substance before; but, after working diligently all this time, I have found that by treating it with sulphuric acid it underwent no change, yet by adding a fragment of bichromate of pota.s.sium a series of blue, violet, purple, and red tints were produced, very similar to those seen in the tests for strychnia.

The same results were brought about, also, by peroxide of lead and black oxide of manganese. I dried the skin of a frog and touched it with a drop of solution containing a single one of the tiny crystals, when strong tetantic convulsions ensued and the animal died in ten seconds.

At last, however, after many other experiments, the idea occurred to me that it was an alkaloid of some plant unknown in modern toxicology. I was, of course, aware of the action of the calabar bean of the West Coast of Africa, the akazga, the datura seeds of India, and such-like poisons, but this was certainly none of these. It was a substance terribly deadly--the only substance that could strike death through the cuticle--utterly unknown to us, yet the most potent of all secret poisons."

"And how did you determine it at last?"

"By a reference I discovered in an ancient Latin treatise on poisons from the old monastery at Pavia, now in the British Museum. It gave me a clue which ultimately led me to establish it as the alkaloid of the vayana bean. This bean, it appears, was used in the tenth and eleventh centuries by a sect of the despotic Arab mystics called the Fatimites, who had made Cairo their capital, and held rule over Syria as well as the northern coast of Africa. The last Fatimite was, at a later date, dethroned by Saladin, conqueror of the Koords, and who opposed Richard the First of England. The poison, introduced from Egypt into Italy, was known to the old alchemists as the most secret means of ridding one of undesirable acquaintances. Its effect, it was stated, was the most curious of any known drug, because, for the time being, it completely altered the disposition of the individual and caused him to give way to all sorts of curious notions and delusions, while at the same time he would be entirely obedient to the will of any second person. Afterwards came fierce delirium, a sensation as though the lower limbs were frozen, complete loss of power, exhaustion, and death. But in modern toxicology even the name of the vayana was lost.

"My first step, therefore, was to seek a.s.sistance of the great botanist who is curator of Kew Gardens, and, after considerable difficulty and many experiments, we both arrived at the conclusion that it was the bean of a small and very rare plant peculiar to the oasis of the Ahir in the south of the Great Sahara. At Kew there was a stunted specimen, but it had never borne fruit, therefore we both searched for any other specimen that might exist in England. We heard of one in the wonderful gardens of La Mortola, near Mentone, and, after diligent inquiries, discovered that a firm of importers in Liverpool had sold a specimen with the beans in pod, which was delivered to a person named Turton, living in Bishop's-wood Road, Highgate, and planted in a small greenhouse there.

I have not been idle," he added with a grin. Then, taking from a drawer in the table before him a photograph, he handed it to me, saying, "I have been able to obtain this photograph of Mrs Turton--the lady who purchased the plant in question."

He held it out to me, and in an instant I recognised the face. It was that of the woman who had crept so silently through the rooms at Atworth--La Gioia!

Briefly, I told him all that had transpired on that night, and declared that I recognised her features, whereat he grunted in satisfaction.

"You have asked me to try and solve the mystery, and I have done so.

You will find this woman living at a house called `Fairmead' in the road I have indicated. I have not only established the cause of the phenomena, but I have, at the same time, rediscovered the most extraordinary and deadly substance known in toxicology. As far as the present case is concerned, my work is finished--I have succeeded in making some of the vayana alkaloid. Here it is?" and, taking a small yellow gla.s.s tube, securely corked and sealed, he handed it to me.

In the bottom I saw half a grain of tiny white crystals. I knew now why he was wearing gloves in his laboratory.

"And have you seen this woman?" I asked the queer old fellow, whose careful investigations had been crowned with such success. "How did you know, on the following day, that it was La Gioia who had come in the guise of a dressmaker?"

"I have seen her, and I have seen the plant. It is from one of the beans which I secured secretly that I have been able to produce that substance. I knew her by overhearing a conversation between Miss Wynd and her cousin on the following morning."

"And the woman is in ignorance that you know the truth?"

"Entirely. I have finished. It is for you now to act as you think fit."

I expressed admiration for his marvellous patience and ingenuity in solving the mystery, and, when I left, it was with the understanding that, if I required his further a.s.sistance he would willingly render it.

CHAPTER THIRTY.

"LA GIOIA."

On the following afternoon, in response to a telegram I had sent to Beryl, she accompanied me to Highgate to face La Gioia. Now that I had such complete evidence of her attempts to poison, I did not fear her, but was determined to elucidate the mystery. Beryl accompanied me rather reluctantly, declaring that, with such power as the woman held, our lives were not safe; but I resolved to take her by surprise, and to risk all. After leaving Hoefer I had sought an interview with the detective Bullen, and he, by appointment, was in the vicinity of the house in question, accompanied by a couple of plain-clothes subordinates.

We stopped our cab in Hampstead Lane, and descending, found that the Bishop's-wood Road was a semicircular thoroughfare of substantial detached houses, the garden of each ab.u.t.ting upon a cricket-ground in the centre, and each with its usual greenhouse where geraniums were potted and stored in winter. On entering the quiet, highly-respectable crescent, we were not long in discovering a house with the name "Fairmead" inscribed in gilt letters upon the gate, while a little further along my eyes caught sight of two scavengers diligently sweeping the road, and, not far away, Bullen himself was walking with his back turned towards me.

On our summons being responded to I inquired for Mrs Turton, and we were shown into the drawing-room--a rather severely furnished apartment which ran through into the greenhouse wherein stood the rare plant.

Hoefer had described it minutely, and while we waited, we both peered into the greenhouse and examined it. The plant standing in the full sunlight was about two feet high, with broad, spreading leaves of a rich, dark green, and grew in an ordinary flower-pot. Half-hidden by the leaves, just as Hoefer had said, we saw some small green pods, long and narrow--the pods of the fatal vayana.

Ere we had time to exchange words the door of the room opened, and there stood before us the tall, dark-robed figure of "La Gioia." Her hard face, pale and expectant, showed in the full light to be that of a woman of perhaps forty, with dark hair, keen, swift eyes, thin cheeks, and bony features--a countenance not exactly ugly, but rather that of a woman whose beauty had prematurely faded owing to the heavy cares upon her.

I was the first to address her, saying, "I think, madam, you are sufficiently well acquainted with both of us not to need any formal introduction."

Her brow contracted and her lips stood apart. Then, without hesitation, I told her my name and that of my companion, while the light died from her careworn face and she stood motionless as one petrified.

"We have come here, to you, to seek the truth of the conspiracy against us--the plot in which you yourself have taken part. We demand to know the reason of the secret attempts you have made upon the lives of both of us."

"I don't understand you," she answered with hauteur.

"To deny it is useless," I said determinedly. "The insidious poison you have used is the vayana, and the only specimen in England bearing fruit is standing there in your greenhouse." And as I uttered those words I closed the door leading beyond, and, locking it, placed the key in my pocket.

Her teeth were firmly set. She glanced at me and tried to deny the allegation, but so utterly was she taken aback by my sudden denunciation that words failed her. A moment later, however, taking several paces forward to where we stood, she cried with a sudden outburst of uncontrollable anger--

"You--Beryl Wynd--I hate you! I swore that you should die, and you shall--you shall!"

But I stepped between them, firm and determined. I saw that this woman was a veritable virago, and that now we had cornered her so neatly she was capable of any crime.

"I demand to know the truth!" I said in a hard, distinct voice.

"You will know nothing from me," she snarled. "That woman has betrayed me!" she added, indicating Beryl.

"Your evil deeds alone have betrayed you," I responded, "and if you decline to tell me anything of your own free will, then perhaps you will make a statement to the police when put upon your trial for attempted murder."

"My trial!" she gasped, turning pale again. "You think to frighten me into telling you something, eh?" she laughed. "Ah! you do not know me."

"I know you sufficiently well to be aware that you are a clever and ingenious woman," I replied. "And in this affair I entertain a belief that our interests may, after all, be mutual."

"How?"

"Tattersett is your enemy, as he is ours." It was a wild shot, but I recollected his words that I had overheard in the park at Whitton.

"There has been a conspiracy against myself and this lady here, who is my wife."

"Your wife!" she gasped.

"I have spoken the truth," I said. "I am here to learn the details from you. If, on the other hand, you prefer to preserve the secret of your accomplices, I shall demand your arrest without delay."

She was silent. Then, after further declarations of ignorance, she was driven to desperation by my threats of arrest, and at last said in a hard, husky voice--

"I must first tell you who and what I am. My father was an English merchant, named Turton, who lived in Palermo, and my mother was Italian.

Fifteen years ago I was a popular dancer, known throughout Italy as `La Gioia.' While engaged at La Scala Theatre, in Milan, I met an Englishman named Ashwicke--"

"Ashwicke?" I exclaimed.

"Not the man whom you know as Ashwicke, but another," she responded.

"He was interested in the occult sciences, apparently wealthy, and much enamoured of me. In the six months of our courtship I learned to love him madly, and the result was that we were married at the Municipio, in Milan, which stands exactly opposite the entrance to the theatre. A month afterwards, however, he decamped with my jewels and the whole of the money I had saved, leaving behind him, as his only personal possessions, a box containing some rare old vellum books which he had purchased somewhere down in the old Tuscan towns, and of which he had been extremely careful. At first I could not believe that he could have treated me thus, after all his professions of love; but as the weeks pa.s.sed and he did not return, I slowly realised the truth that I had been duped and deserted. It was then that I made a vow of revenge.