"Then how do you explain Mr. Langley's death?" demanded Harrington. "My theory of a spark from a cigar may be true, after all."

"I am coming to that in a moment," answered Kennedy quietly. "My first suspicion was aroused by what not even Doctor Putnam seems to have noticed. The skull of Mr. Langley, charred and consumed as it was, seemed to show marks of violence. It might have been from a fracture of the skull or it might have been an accident to his remains as they were being removed to the anteroom. Again, his tongue seemed as though it was protruding. That might have been natural suffocation, or it might have been from forcible strangulation. So far I had nothing but conjecture to work on. But in looking over the living-room I found near the table, on the hardwood floor, a spot--just one little round spot. Now, deductions from spots, even if we know them to be blood, must be made very carefully. I did not know this to be a blood-spot, and so was very careful at first.

"Let us a.s.sume it was a blood-spot, however. What did it show? It was just a little regular round spot, quite thick. Now, drops of blood falling only a few inches usually make a round spot with a smooth border. Still the surface on which the drop falls is quite as much a factor as the height from which it falls. If the surface is rough the border may be irregular. But this was a smooth surface and not absorbent. The thickness of a dried blood-spot on a non-absorbent surface is less the greater the height from which it has fallen. This was a thick spot. Now if it had fallen, say, six feet, the height of Mr.

Langley, the spot would have been thin--some secondary spatters might have been seen, or at least an irregular edge around the spot.

Therefore, if it was a blood-spot, it had fallen only one or two feet.

I ascertained next that the lower part of the body showed no wounds or bruises whatever.

"Tracks of blood such as are left by dragging a bleeding body differ very greatly from tracks of arterial blood which are left when the victim has strength to move himself. Continuing my speculations, supposing it to be a blood-spot, what did it indicate? Clearly that Mr. Langley was struck by somebody on the head with a heavy instrument, perhaps in another part of the room, that he was choked, that as the drops of blood oozed from the wound on his head, he was dragged across the floor, in the direction of the fireplace--"

"But, Professor Kennedy," interrupted Doctor Putnam, "have you proved that the spot was a blood-spot? Might it not have been a paint-spot or something of that sort?"

Kennedy had apparently been waiting for just such a question.

"Ordinarily, water has no effect on paint," he answered. "I found that the spot could be washed off with water. That is not all. I have a test for blood that is so delicately sensitive that the blood of an Egyptian mummy thousands of years old will respond to it. It was discovered by a German scientist, Doctor Uhlenhuth, and was no longer ago than last winter applied in England in connection with the Clapham murder.

The suspected murderer declared that stains on his clothes were only spatters of paint, but the test proved them to be spatters of blood.

Walter, bring in the cage with the rabbits."

I opened the door and took the cage from the groom, who had brought it up from the stable and stood waiting with it some distance away.

"This test is very simple, Doctor Putnam," continued Craig, as I placed the cage on the table and Kennedy unwrapped the sterilised test-tubes.

"A rabbit is inoculated with human blood, and after a time the serum that is taken from the rabbit supplies the material for the test.

"I will insert this needle in one of these rabbits which has been so inoculated and will draw off some of the serum, which I place in this test-tube to the right. The other rabbit has not been inoculated. I draw off some of its serum and place that tube here on the left--we will call that our 'control tube.' It will check the results of our tests.

"Wrapped up in this paper I have the sc.r.a.pings of the spot which I found on the floor--just a few grains of dark, dried powder. To show how sensitive the test is, I will take only one of the smallest of these minute sc.r.a.pings. I dissolve it in this third tube with distilled water.

I will even divide it in half, and place the other half in this fourth tube.

"Next I add some of the serum of the uninoculated rabbit to the half in this tube. You observe, nothing happens. I add a little of the serum of the inoculated rabbit to the other half in this other tube. Observe how delicate the test is--"

Kennedy was leaning forward, almost oblivious of the rest of us in the room, talking almost as if to himself. We, too, had riveted our eyes on the tubes.

As he added the serum from the inoculated rabbit, a cloudy milky ring formed almost immediately in the hitherto colourless, very dilute blood-solution.

"That," concluded Craig, triumphantly holding the tube aloft, "that conclusively proves that the little round spot on the hardwood floor was not paint, was not anything in this wide world but blood."

No one in the room said a word, but I knew there must have been someone there who thought volumes in the few minutes that elapsed.

"Having found one blood-spot, I began to look about for more, but was able to find only two or three traces where spots seemed to have been.

The fact is that the blood spots had been apparently carefully wiped up.

That is an easy matter. Hot water and salt, or hot water alone, or even cold water, will make quite short work of fresh blood-spots--at least to all outward appearances. But nothing but a most thorough cleaning can conceal them from the Uhlenhuth test, even when they are apparently wiped out. It is a case of Lady Macbeth over again, crying in the face of modern science, 'Out, out, d.a.m.ned spot.'

"I was able with sufficient definiteness to trace roughly a course of blood-spots from the fireplace to a point near the door of the living-room. But beyond the door, in the hall, nothing."

"Still," interrupted Harrington, "to get back to the facts in the case.

They are perfectly in accord either with my theory of the cigar or the Record's of spontaneous combustion. How do you account for the facts?"

"I suppose you refer to the charred head, the burned neck, the upper chest cavity, while the arms and legs were untouched?"

"Yes, and then the body was found in the midst of combustible furniture that was not touched. It seems to me that even the spontaneous-combustion theory has considerable support in spite of this very interesting circ.u.mstantial evidence about blood-spots. Next to my own theory, the combustion theory seems most in harmony with the facts."

"If you will go over in your mind all the points proved to have been discovered--not the added points in the Record story--I think you will agree with me that mine is a more logical interpretation than spontaneous combustion," reasoned Craig. "Hear me out and you will see that the facts are more in harmony with my less fanciful explanation.

No, someone struck Lewis Langley down either in pa.s.sion or in cold blood, and then, seeing what he had done, made a desperate effort to destroy the evidence of violence. Consider my next discovery."

Kennedy placed the five gla.s.ses which I had carefully sealed and labelled on the table before us.

"The next step," he said, "was to find out whether any articles of clothing in the house showed marks that might be suspected of being blood-spots. And here I must beg the pardon of all in the room for intruding in their private wardrobes. But in this crisis it was absolutely necessary, and under such circ.u.mstances I never let ceremony stand before justice.

"In these five gla.s.ses on the table I have the washings of spots from the clothing worn by Tom, Mr. James Langley, Junior, Harrington Brown, and Doctor Putnam. I am not going to tell you which is which--indeed I merely have them marked, and I do not know them myself. But Mr. Jameson has the marks with the names opposite on a piece of paper in his pocket.

I am simply going to proceed with the tests to see if any of the stains on the coats were of blood."

Just then Doctor Putnam interposed. "One question, Professor Kennedy.

It is a comparatively easy thing to recognise a blood-stain, but it is difficult, usually impossible, to tell whether the blood is that of a man or of an animal. I recall that we were all in our hunting-jackets that day, had been all day. Now, in the morning there had been an operation on one of the horses at the stable, and I a.s.sisted the veterinary from town. I may have got a spot or two of blood on my coat from that operation. Do I understand that this test would show that?"

"No," replied Craig, "this test would not show that. Other tests would, but not this. But if the spot of human blood were less than the size of a pin-head, it would show--it would show if the spot contained even so little as one twenty-thousandth of a gram of alb.u.min. Blood from a horse, a deer, a sheep, a pig, a dog, could be obtained, but when the test was applied the liquid in which they were diluted would remain clear. No white precipitin, as it is called, would form. But let human blood, ever so diluted, be added to the serum of the inoculated rabbit, and the test is absolute."

A death-like silence seemed to pervade the room. Kennedy slowly and deliberately began to test the contents of the gla.s.ses. Dropping into each, as he broke the seal, some of the serum of the rabbit, he waited a moment to see if any change occurred.

It was thrilling. I think no one could have gone through that fifteen minutes without having it indelibly impressed on his memory. I recall thinking as Kennedy took each gla.s.s, "Which is it to be, guilt or innocence, life or death?" Could it be possible that a man's life might hang on such a slender thread? I knew Kennedy was too accurate and serious to deceive us. It was not only possible, it was actually a fact.

The first gla.s.s showed no reaction. Someone had been vindicated.

The second was neutral likewise--another person in the room had been proved innocent.

The third--no change. Science had released a third.

The fourth--

Almost it seemed as if the record in my pocket burned--spontaneously--so intense was my feeling. There in the gla.s.s was that fatal, telltale white precipitate.

"My G.o.d, it's the milk ring!" whispered Tom close to my ear.

Hastily Kennedy dropped the serum into the fifth. It remained as clear as crystal.

My hand trembled as it touched the envelope containing my record of the names.

"The person who wore the coat with that blood-stain on it," declared Kennedy solemnly, "was the person who struck Lewis Langley down, who choked him and then dragged his scarcely dead body across the floor and obliterated the marks of violence in the blazing log fire. Jameson, whose name is opposite the sign on this gla.s.s?"

I could scarcely tear the seal to look at the paper in the envelope. At last I unfolded it, and my eye fell on the name opposite the fatal sign.

But my mouth was dry, and my tongue refused to move. It was too much like reading a death-sentence. With my finger on the name I faltered an instant.

Tom leaned over my shoulder and read it to himself. "For Heaven's sake, Jameson," he cried, "let the ladies retire before you read the name."

"It's not necessary," said a thick voice. "We quarrelled over the estate. My share's mortgaged up to the limit, and Lewis refused to lend me more even until I could get Isabelle happily married. Now Lewis's goes to an outsider--Harrington, boy, take care of Isabelle, fortune or no fortune. Good--"

Someone seized James Langley's arm as he pressed an automatic revolver to his temple. He reeled like a drunken man and dropped the gun on the floor with an oath.

"Beaten again," he muttered. "Forgot to move the ratchet from 'safety'