"Then you will get the stuff together this morning and have it up to my place this afternoon."

"Yes, Professor, yes. It is a bargain. I would do anything for Mrs.

Popper--she is a fine woman."

Late that afternoon I rejoined Craig at his laboratory. Signor Marina had already arrived with a truck and was disposing the paraphernalia about the laboratory. He had first laid a thick black rug. Mrs. Popper very much affected black carpets, and I had noticed that Vandam's room was carpeted in black, too. I suppose black conceals everything that one oughtn't to see at a seance.

A cabinet with a black curtain, several chairs, a light deal table, several banjos, horns, and other instruments were disposed about the room. With a few suggestions from me we made a fair duplication of the hangings on the walls. Kennedy was manifestly anxious to finish, and at last it was done.

After Marina had gone, Kennedy stretched a curtain over the end of the room farthest from the cabinet. Behind it he placed on a shelf the apparatus composed of the pendulums and magnets. The beakers and test-tubes were also on this shelf.

He had also arranged that the cabinet should be so situated that it was next a hallway that ran past his laboratory.

"To-night, Jameson," he said, indicating a spot on the hall wall just back of the cabinet, "I shall want you to bring my guests out here and do a little spirit rapping--I'll tell you just what to do when the time comes."

That night, when we gathered in the transformed laboratory, there were Henry Vandam, Dr. Hanson, Inspector O'Connor, Kennedy, and myself.

At last the sound of wheels was heard, and Mrs. Popper drove up in a hansom, accompanied by Farrington. They both inspected the room narrowly and seemed satisfied. I had, as I have said, taken a serious dislike to the man, and watched him closely. I did not like his air of calm a.s.surance.

The lights were switched off, all except one sixteen-candle-power lamp in the farthest corner, shaded by a deep-red globe. It was just light enough to see to read very, large print with difficulty.

Mrs. Popper began immediately with the table. Kennedy and I sat on her right and left respectively, in the circle, and held her hands and feet.

I confess to a real thrill when I felt the light table rise first on two legs, then on one, and finally remain suspended in the air, whence it dropped with a thud, as if someone had suddenly withdrawn his support.

The medium sat with her back to the curtain of the cabinet, and several times I could have sworn that a hand reached out and pa.s.sed close to my head. At least it seemed so. The curtain bulged at times, and a breeze seemed to sweep out from the cabinet.

After some time of this sort of work Craig led gradually up to a request for a materialisation of the control of Vandam, but Mrs. Popper refused.

She said she did not feel strong enough, and Farrington put in a hasty word that he, too, could feel that "there was something working against them." But Kennedy was importunate and at last she consented to see if "John" would do some rapping, even if he could not materialise.

Kennedy asked to be permitted to put the questions.

"Are you the 'John' who appears to Mr. Vandam every night at twelve-thirty?"

Rap! rap! rap! came the faint reply from the cabinet. Or rather it seemed to me to come from the floor near the cabinet, and perhaps to be a trifle m.u.f.fled by the black carpet.

"Are you in communication with Mrs. Vandam?"

Rap! rap! rap!

"Can she be made to rap for us?"

Rap! rap!

"Will you ask her a question and spell out her answer?"

Rap! rap! rap!

Craig paused a moment to frame the question, then shot it out point-blank: "Does Mrs. Vandam know now in the other world whether anyone in this room subst.i.tuted a morphine capsule for one of those ordered by her three days before she died? Does she know whether the same person has done the same thing with those later ordered by Mr.

Vandam?"

"John" seemed considerably perturbed at the mention of capsules. It was a long time before any answer was forthcoming. Kennedy was about to repeat the question when a faint sound was heard.

Rap!----

Suddenly came a wild scream. It was such a scream as I had never heard before in my life. It came as though a dagger had been thrust into the heart of Mrs. Popper. The lights flashed up as Kennedy turned the switch.

A man was lying flat on the floor--it was Inspector O'Connor. He had succeeded in slipping noiselessly, like a snake, below the curtain into the cabinet. Craig had told him to look out for wires or threads stretched from Mrs. Popper's clothing to the bulging curtain of the cabinet. Imagine his surprise when he saw that she had simply freed her foot from the shoe, which I was carefully holding down, and with a backward movement of the leg was reaching out into the cabinet behind her chair and was doing the rapping with her toes.

Lying on the floor he had grasped her foot and caught her heel with a firm hand. She had responded with a wild yell that showed she knew she was trapped. Her secret was out.

Hysterically Mrs. Popper began to upbraid the inspector as he rose to his feet, but Farrington quickly interposed.

"Something was working against us to-night, gentlemen. Yet you demanded results. And when the spirits will not come, what is she to do? She forgets herself in her trance; she produces, herself, the things that you all could see supernaturally if you were in sympathy."

The mere sound of Farrington's voice seemed to rouse in me all the animosity of my nature. I felt that a man who could trump up an excuse like that when a person was caught with the goods was capable of almost anything.

"Enough of this fake seance," exclaimed Craig. "I have let it go on merely for the purpose of opening the eyes of a certain deluded gentleman in this room. Now, if you will all be seated I shall have something to say that will finally establish whether Mary Vandam was the victim of accident, suicide, or murder."

With hearts beating rapidly we sat in silence.

Craig took the beakers and test-tubes from the shelf behind the curtain and placed them on the little deal table that had been so merrily dancing about the room.

"The increasing frequency with which tales of murder by poison appear in the newspapers," he began formally, "is proof of how rapidly this new civilisation of ours is taking on the aspects of the older civilisations across the seas. Human life is cheap in this country; but the ways in which human life has been taken among us have usually been direct, simple, aboveboard, in keeping with our democratic and pioneer traditions. The pistol and the bowie-knife for the individual, the rope and the torch for the mob, have been the usual instruments of sudden death. But when we begin to use poisons most artfully compounded in order to hasten an expected bequest and remove obstacles in its way--well, we are practising an art that calls up all the memories of sixteenth century Italy.

"In this beaker," he continued, "I have some of the contents of the stomach of the unfortunate woman. The coroner's physician has found that they show traces of morphine. Was the morphine in such quant.i.ties as to be fatal? Without doubt. But equally without doubt a.n.a.lysis could not discover and prove it in the face of one inconsistency. The usual test which shows morphine poisoning failed in this case. The pupils of her eyes were not symmetrically contracted. In fact they were normal.

"Now, the murderer must have known of this test. This clever criminal also knew that to be successful in the use of this drug where others had failed, the drug must be skilfully mixed with something else. In that first box of capsules there were six. The druggist compounded them correctly according to the prescription. But between the time when they came into the house from the druggist's and the time when she took the first capsule, that night, someone who had access to the house emptied one capsule of its harmless contents and refilled it with a deadly dose of morphine--a white powder which looks just like the powder already in the capsules.

"Why, then, the normal pupils of the eyes? Simply because the criminal put a little atropine, or belladonna, with the morphine. My tests show absolutely the presence of atropine, Dr. Hanson," said Craig, bowing to the physician.

"The best evidence, however, is yet to come. A second box of six capsules, all intact, was discovered yesterday in the possession of Henry Vandam. I have a.n.a.lysed the capsules. One contains no quinine at all--it is all morphine and atropine. It is, without doubt, precisely similar to the capsule which killed Mrs. Vandam. Another night or so, and Henry Vandam would have died the same death."

The old man groaned. Two such exposures had shaken him. He looked from one of us to another as if not knowing in whom he could trust. But Kennedy hurried on to his next point.

"Who was it that gave the prescription to Mrs. Vandam originally? She is dead and cannot tell. The others won't tell, for the person who gave her that prescription was the person who later subst.i.tuted the fatal capsule in place of the harmless. The original prescription is here. I have been able to discover from it nothing at all by examining the handwriting.

Nor does the texture of the paper indicate anything to me. But the ink--ah, the ink.

"Most inks seem very similar, I suppose, but to a person who has made a study of the chemical composition of ink they are very different. Ink is composed of iron tannate, which on exposure to air gives the black of writing. The original pigment--say blue or blue-black ink--is placed in the ink, to make the writing visible at first, and gradually fades, giving place to the black of the tannate which is formed. The dyestuffs employed in the commercial inks of to-day vary in colour from pale greenish blue to indigo and deep violet. No two give identical reactions--at all events not when mixed with the iron tannate to form the pigment in writing.

"It is owing to the difference in these provisional colouring matters that it is possible to distinguish between writing written with different kinds of ink. I was able easily to obtain samples of the inks used by the Vandams, by Mrs. Popper, by Mr. Farrington, and by the druggist. I have compared the writing of the original prescription with a colour scale of my own construction, and I have made chemical tests. The druggist's ink conforms exactly to the writing on the two pill-boxes, but not to the prescription. One of the other three inks conforms by test absolutely to the ink in that prescription signed 'Dr.

C. W. H.' as a blind. In a moment my chain of evidence against the owner of that bottle of ink will be complete."

I could not help but think of the two pendulums on the shelf behind the curtain, but Craig said nothing for a moment to indicate that he referred to that apparatus. We sat dazed. Farrington seemed nervous and ill at ease. Mrs. Popper, who had not recovered from the hysterical condition of her exposure, with difficulty controlled her emotion.

Vandam was crushed.

"I have not only arranged this laboratory so as to reproduce Mrs.

Popper's seance-room," began Craig afresh, "but I have had the cabinet placed in relatively the same position a similar cabinet occupies in Mr.

Vandam's private seance-room in the Vandam mansion.

"One night, Mr. Jameson and myself were visiting Mr. Vandam. At precisely twelve-thirty we heard most unaccountable rappings from that cabinet. I particularly noted the position of the cabinet. Back of it ran a hallway. That is duplicated here. Back of this cabinet is a hallway. I had heard of these rappings before we went, but was afraid that it would be impossible for me to catch the ghost red handed. There is a limit to what you can do the first time you enter a man's house, and, besides, that was no time to arouse suspicion in the mind of anyone. But science has a way out of every dilemma. I determined to learn something of these rappings."